Dissertations / Theses on the topic 'Flavor and odor'

Thesis (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Aged distilled spirits such as whiskey are complex mixtures of flavour compounds in an ethanol-water matrix. The flavour compounds involved can have widely different volatility and relative amounts. Many of the organoleptic properties that make whiskey suitable for commercial sale have their origin in reactions occurring during the ageing process in oak wood barrels. To investigate the complex changes that take place during spirit ageing a preparative fractional vacuum distillation process was developed. Both high and low volatility compounds could be individually isolated as fractions and free from both the ethanol matrix and the fermentation fusel alcohols. This allowed a range of sensory and analytical procedures to be conducted on these fractions, in particular to investigate changes occurring during ageing. Gas chromatographic (GC) analysis of the low volatility fraction is complicated by the fact that both the compounds and their ethanol matrix have very similar chromatographic behaviour when separated simultaneously on standard chromatographic phases. Compound and matrix co-elution becomes a major problem and conditions for mass spectrometric (MS) investigation are disadvantageous. A two-dimensional GC configuration using dissimilar chromatographic phases was configured to overcome these limitations. Using this approach 27 compounds were separated and identified. Headspace injection was used to increase detection sensitivity. Changes with ageing for seven compounds present at very low levels were quantified. In addition changes in the most abundant compounds were quantified by standard split injection, and changes in trace level sulfur compounds by headspace injection with sulfur chemiluminescent detection (SCD). Increases of the concentrations of pleasant fruity ethyl esters and acetates were established. Volatile sulfides with generally objectionable aroma showed concomitant major decreases. Appropriate techniques could also be applied to the low volatility compounds recovered from the whiskey water fraction. High temperature GC-MS analysis of an extract of the water fraction allowed the identification of 30 compounds. Three phenolic esters were identified in whiskey for the first time. These compounds were synthesised and shown to be contributory to desirable ageing flavour. Increases in concentrations of 16 oak derived compounds during alO year ageing period were established. Several compounds increased significantly over this time period. Ratios of aromatic phenolic aldehydes, and changes in these ratios during ageing, were unique to the type of barrel used in these experiments. This suggests that the final sensory properties of aged whiskey may be more dependent on wood parameters than previously thought. Preparative reverse phase High Pressure Liquid Chromatography (HPLC) with an ethanol water gradient was used to further fractionate an extract of the low volatility compounds. Subsequent analysis and sensory testing allowed a group separation of compounds with each group contributing characteristic attributes to the total flavour. One group contained the three new phenolic esters together with a number of other unidentified compounds. This group was found to be important for desirable ageing flavour that seems to develop slowly with time. Further studies in this area to understand the individual and synergistic contributions of the many facets of ageing chemistry will have important commercial implications.
AFRIKAANSE OPSOMMING: Verouderde spiritus soos Whiskey is 'n komplekse mengsel van geurstowwe in 'n etanolwater oplossing. Die vlugtigheid van die geurstowwe asook die konsentrasies waarin hul aanwesig is, varieer aansienlik. Verskeie van die sintuiglike eienskappe wat kommersiële waarde aan whiskey verleen, het huloorsprong in reaksies wat tydens die verouderingsproses in eikehoutvate plaasvind. Ten einde die ingewikkelde veranderinge wat tydens die veroudering van spiritus plaasvind, te ondersoek, is 'n preparatiewe fraksionele vakuumdistillasieproses ontwikkel. Hoogs vlugtige en minder vlugtige verbindings kon geskei word in afsonderlike fraksies wat vry was van etanol en fuselalkohole. Dit het die sintuiglike en fisies-chemiese analises van die fraksies moontlik gemaak, veralom die veranderings wat tydens veroudering plaasvind, te ondersoek. Gaschromatografiese (GC) analise van die fraksie met 'n lae vlugtigheid word gekompliseer deur die feit dat hierdie komponente en die etanol waarin dit opgelos is soortgelyke chromatografiese eienskappe toon wanneer hul gelyktydig op standaard gaschromatografie fases geskei word. Die gelyktydige eluering van dié komponente en etanol waarin hul opgelos is, skep 'n probleem wat nadelig vir massaspektrometriese (MS) analise is. Die beperkings is oorkom deur die gebruik van tweedimensionele GC en stasionêre fases met uiteenlopende eienskappe. Op dié wyse is 27 verbindings geskei en geïdentifiseer. Die veranderinge in konsentrasies tydens veroudering is vir sewe verbindings gekwantifiseer. Veranderinge in die konsentrasies van die verbindings teenwoordig in die hoogste konsentrasies is gekwantifiseer deur split-inspuitings, terwyl veranderinge in die spoorkonsentrasies van vlugtige swawelverbindings mbv dampfase-inspuitings en met swawel chemolumisensie deteksie (SCD) bepaal is. Toenames in die konsentrasies van die aangename vrugtige esters en asetate is bepaal. Vlugtige sulfiede met meesalonaanvaarbare aromas toon gelyktydige groot afnames. Geskikte tegnieke is ook gebruik vir die herwinning van minder vlugtige verbindings met die waterfase van whiskey. Hoë temperatuur GC-MS analises van 'n ekstrak van die waterfase het die identifikasie van 30 komponente moontlik gemaak. Drie fenoliese esters is vir die eerste keer in whiskey gevind. Hierdie verbindings is gesintetiseer en hul bydrae tot die gewenste verouderingsgeur is sintuiglik bevestig. Toenames in die konsentrasies van 16 eikehoutverwante verbindings gedurende 'n verouderingsperiode van 10 jaar is bepaal. 'n Betekenisvolle toename het voorgekom in die konsentrasies van verskeie van hierdie whiskey verbindings. Die verhoudings van aromatiese fenoliese aldehiede en die verandering in die verhoudings tydens veroudering was kenmerkend van die tipe eikehoutvat wat gebruik is. Dié bevinding dui daarop dat die fenole sintuiglike eienskappe van verouderde whiskey meer afhanklik mag wees van eikehout parameters as wat voorheen algemeen aanvaarbaar is. Preparatiewe omgekeerde fase hoëdrukvloeistofchromatografie met etanol/water as 'n gradient elueermiddel is gebruik om 'n ekstrak van die minder vlugtige verbindings verder te fraksioneer. Verdere GC-, MS- en sintuiglike analise het die skeiding van groepe van verbindings waarvan elk kenmerkende bydraes tot die totale geur lewer, moontlik gemaak. Een groep het drie nuut geïdentifiseerde fenoliese esters, tesame met 'n aantal ongeïdentifiseerde verbindings, bevat. Daar is vasgestel dat hierdie groep 'n belangrike bydrae maak tot die gewenste geur wat klaarblyklik stadig tydens veroudering ontwikkel. Verdere ondersoeke in hierdie verband om die individuele en sinergistiese bydraes van verskeie fasette van die chemie van veroudering te verstaan, kan belangrike kommersiële implikasies hê.

Thesis (PhD)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Yeasts produce a broad range of aroma-active volatile esters and higher alcohols during alcoholic fermentation. Some of these esters and higher alcohols are important for the fruity flavors and therefore the final quality of wine and other fermented beverages. Esters are produced and hydrolyzed by alcohol acetyltransferases and esterases, respectively. In yeast, ester-synthesizing activities are represented by two alcohol acetyltransferases encoded by the ATFI and ATF2 genes, and by an ethanol hexanoyl transferase encoded by the EHTI gene. Atfl p and Atf2p appear responsible for the production of ethyl acetate and isoamyl acetate, while Ehtl p synthesizes ethyl hexanoate from ethanol and hexanoyl-CoA. Although a fair amount of information is available regarding the ATF 1 gene, limited information is available on the remaining alcohol acetyltransferases. Only two genes that code for esterases have been identified in yeast, namely lAHI and TIPI. It has also been shown that the balance between alcohol acetyltransferases and esterases is important for the net rate of ester accumulation. Higher alcohols are synthesized from the a-keto-acids in the branched-chain amino acid metabolic pathway by decarboxylation and reduction. The transamination of the amino acid to the respective a-keto-acid is catalyzed by mitochondrial and cytosolic branched-chain amino acid transferases, which are encoded by the BATI and BAT2 genes, respectively. In recent years, a strong scientific and industrial interest in the metabolism of flavoractive compounds has emerged, but information regarding the roles of specific enzymes and the physiological relevance of their metabolism remains limited. The aim of this project was to investigate the physiological and metabolic consequences of changes in the expression levels of some of the key enzymes involved in aroma compound production. The consequences of these changes on the chemical composition and the fermentation bouquet of wines and distillates were also investigated. The first part of the section on the results in this dissertation reports on the role and relative importance of the Saccharomyces cerevisiae enzymes involved in ester metabolism, namely Atflp, Atf2p, Ehtlp, Iahlp and Tiplp. The corresponding genes were overexpressed in a laboratory strain of S. cerevisiae, BY4742, and in a widely used commercial wine yeast strain, VIN13. Table wine and base wines for distillation were prepared with these VIN13 transformed strains. The ester concentrations and aroma profiles of the wines and distillates were analyzed and compared. The data indicated that the overexpression of ATF 1 and ATF2 increased the concentrations of ethyl acetate, isoamyl acetate, 2-pheylethyl acetate and ethyl caproate, while the overexpression of JAHI resulted in a significant decrease in the concentrations of ethyl acetate, isoamyl acetate, hexyl acetate and 2-phenylethyl acetate. The overexpression of EHTI resulted in a marked increase in the concentrations of ethyl caproate, ethyl caprylate and ethyl caprate, while the overexpression of TJP1 did not decrease the concentrations of any of the esters. In most cases, there was a correlation between the increase in esters and the decrease in higher alcohols. The data suggest that yeast balances the amount of different esters produced through alcohol acetyltransferases and esterases, and that, in some cases, these enzymes appear to overlap in function and/or influence each other's activity. In the second part of the results section, the consequences of the deletion and the overexpression of two genes, BATl and BAT2, which encode transaminases that contribute to the metabolism of higher alcohols, were investigated. The genes were both disrupted in a S. cerevisiae BY4742, and overexpressed in both this laboratory strain and in the VIN13 wine yeast strain. The effects of these modifications on the general physiology of the corresponding yeast strains and on higher alcohol metabolism were assessed in a range of growth conditions, including aerobic and anaerobic growth conditions, in the presence of glucose or raffinose as sole carbon source and growth in the presence of various concentrations of amino acids. Table wine and base wines for distillation were prepared with the modified industrial strains and the concentrations of the higher alcohols and the aroma profiles of the wine and distillates were analyzed and compared. Batl deletion seemed to be lethal under the conditions that were created, and therefore only the bat2!:!.strain, together with the BATI and BAT2 overexpression strains, were investigated. These modifications did not appear to significantly affect the general physiology of the strains. The results obtained indicated that the overexpression of BATI increased the concentrations of isoamyl alcohol and isoamyl acetate, and, to a lesser extent, the concentrations of isobutanol and isobutyric acid. The overexpression of the BAT2 gene resulted in a substantial increase in the levels of isobutanol, isobutyric acid and propionic acid production, and a modest increase in the level of propanol and isovaleric acid. Interestingly, the overexpression of BAT2 led to a decrease in isoamyl alcohol and isoamyl acetate concentrations. Sensory analyses indicated that the wines and distillates produced with the strains in which the BATl and BAT2 genes were overexpressed had more fruity characteristics (peach and apricot aromas) than the wines produced by the wild-type strains. This study offers new prospects for the development of wine yeast starter strains with optimized ester and higher alcohol-producing capability that could assist winemakers in their efforts to consistently produce wine to definable specifications and styles and a predetermined flavor profile.
AFRIKAANSE OPSOMMING: Gedurende fermentasie produseer giste 'n wye verskeidenheid vlugtige aromatiese esters en hoër alkohole. Sommige van hierdie esters en hoër alkohole is belangrik vir die vrugtige geure en dra dus by tot die finale kwaliteit van wyn en ander gefermenteerde drankies. Esters word onderskeidelik deur alkoholasetieltranferases en esterases geproduseer en gehidroliseer. In giste word die ester-sintetiserende aktiwiteite deur twee alkoholasetieltransferases verteenwoordig wat deur die ATFI-en ATF2-gene, asook 'n etanolheksanoïeltransferase wat deur die EHTl-geen, gekodeer word. Dit blyk dat ATFlp en ATF2p verantwoordelik is vir die produksie van etielasetaat en isoamielasetaat, terwyl Ehtl p-etielheksanoaat vanaf etanol en heksanoïel-CoA sintetiseer. Alhoewel daar 'n redelike hoeveelheid inligting t.o.v die ATF I-geen beskikbaar is, is daar weinig inligting oor die res van die aloholasetieltransferases. Slegs twee gene wat vir esterases kodeer, is in gis geïdentifiseer, naamlik IAHI en TIPI. Daar is ook bewys dat 'n balans tussen die alkoholasetieltransferases en esterases baie belangrik is vir die netto-tempo van ester-akkumulasie. Hoër alkohole word gesintetiseer vanaf a-keto sure in die vertakte-ketting aminosuur metaboliese pad deur dekarboksilasie en reduksie. Die transaminasie van die aminosuur na die onderkeidelike a-ketosuur word deur vertakte-ketting aminosuur transferases, geleë in die mitochondrion en sitosol, en gekodeer deur BATl- en BAT2-gene, gekataliseer. In die laaste paar jare het daar 'n sterk wetenskaplike, asook industrïele, belangstelling in die metabolisme van aroma-aktiewe komponente te voorskyn gekom, maar inligting in verband met die rol van spesifieke ensieme en die fisiologiese belangrikheid van hul metabolisme is egter beperk. Die doel van hierdie projek was om die fisiologiese en metaboliese gevolge van veranderinge in die ekspressievlakke van sommige sleutelensieme betrokke by aromakomponent-produksie te ondersoek. Die gevolge van hierdie veranderinge op chemiese vlakke, asook hoe die fermentasie-aroma van die wyne en distillate beïnvloed word, is ook bestudeer. Die eerste gedeelte van die resultate rapporteer oor die rol en relatiewe belangrikheid van die Saccharomyces cerevisiae-ensieme betrokke by estermetabolisme, naamlik Atfl p, Atf2p, Ehtlp, Iahlp en Tiplp. Die gene was ooruitgedruk in 'n laboratoriurnras van S. cerevisiae, BY4742, asook in 'n kommersïele wyngisras, VIN13. Tafelwyne en basiswyne vir distillasie is gemaak met die getransformeerde VIN13-rasse. Die esterkonsentrasies en aromaprofiele van die wyne en distillate is ontleed en vergelyk. Die data het gewys dat die ooruitdrukking van ATFI- en ATF2-gene 'n verhoging in etielasetaat, isoamielasetaat, 2-fenieletielasetaat en etielkaproaat veroorsaak het, terwyl ooruitdrukking van !AHI 'n betekenisvolle afname in etielasetaat-, isoamielasetaat-, heksielasetaat- en 2-fenieletielasetaat-konsentrasies veroorsaak het. Die ooruitdrukking van EHTI het 'n duidelike verhoging in etielkaproaat, etielkaprilaat en etielkapraat veroorsaak en die ooruitdrukking van TIPIhet geen van die esterkonsentrasies verander nie. In die meeste gevalle was daar nie 'n korrelasie tussen die toename in esters en afname in hoër alkohole nie. Die data stelook voor dat die gis 'n balans tussen die verskillende esters handhaaf deur middel van die alkoholasetieltrasferases en esterases, en in sommige gevalle blyk dit dat die ensieme dieselfde funksies het en/of mekaar se aktiwiteit beïnvloed. In die tweede gedeelte van die resultate is die oorsake van delesie en ooruitdrukking van twee gene, BAT1 en BAT2, wat kodeer vir transaminases wat tot hoër alkohol metabolisme bydra, bestudeer. Die gene is uitgeslaan in S. cerevisiae BY4742 en ooruitgedruk in BY4742 en in die wyngisras VIN13. Die effekte van hierdie modifikasies op die algemene fisiologie van die verskillende gisrasse en op hoëralkoholmetabolisme is onder 'n verskeidenheid kondisies bestudeer, naamlik aërobies en anaërobiese groeikondisies, in die teenwoordigheid van glukose of raffinose as die enigste koolstofbron, asook in die teenwoordigheid van 'n verskeidenheid konsentrasies aminosure. Tafelwyne en basiswyne vir distillasie is gemaak met die gemodifiseerde industrïele rasse en die konsentrasies van die hoër alkohole en aromaprofiele van die wyne en distillate is ontleed en vergelyk. Bat1-delesie was dodelik onder die kondisies, daarom is slegs die batlts-tes tesame met die BAT1 en BAT2 wat in die rasse ooruitgedruk is, bestudeer. Die modifikasies het nie 'n beduidende effek op die algemene fisiologie van die rasse getoon nie. Die data het wel getoon dat die ooruitdrukking van BAT1 'n verhoging in isoamielalkohol- en isoamielasetaatkonsentrasies, en tot 'n mindere mate isobutielalkohol- en isobottersuur-konsentrasies, veroorsaak het. Die ooruitdrukking van BAT2 het 'n beduidende toename in isobutanol-, isobottersuur- en propioonsuurkonsentrasies en 'n kleinere toename in propanol- en isovaleriaansuur veroorsaak. Die ooruitdrukking van BAT2 het ook gelei tot 'n afname in isoamielalkohol- en isoamielasetaatkonsentrasies. Sensoriese analises het getoon dat die wyne en distillate wat geproduseer is met die rasse waarin die BAT1 en BAT2 gene ooruitgedruk is meer vrugtige eienskappe (perske- en appelkoos-aromas) getoon het as die wyne wat deur die wildetipe rasse geproduseer is. Die studie lewer nuwe vooruitsigte vir die ontwikkeling van wyngiste met geoptimiseerde ester en hoër alkohol produserende eienskappe wat die wynmakers in staat kan stelom wyne te produseer met gedefinieerde spesifikasies en style en 'n voorafbepaalde aromaprofiel.

Hops (Humulus lupulus L.) are an indispensable component of beer, with the essential oil responsible for imparting distinctive odour and aroma characteristics to beer. However, not all character-impact odorants in hop essential oil have been identified and hop aroma in beer is still not completely understood. The composition of hop essential oil is very complex with 485 compounds currently identified in the literature, and recent research suggests that up to 1000 compounds may actually be present. Only a certain number will be present at concentrations above threshold and make a direct contribution to the odour of the oil. In addition, many important odorants are only present at trace concentrations. Gas chromatography-olfactometry (GC-O) using human assessors is the best way to locate potent odorants and facilitate their identification. A novel methodology was developed to identify the character-impact odorants in hop essential oil samples using hyphenated techniques in gas chromatography. GC-O was used to locate odour active compounds and determine relative importance using CharmAnalysis[TM] according to the odour potency principle. Due to the chemical complexity of the samples, considerable co-elution of peaks occurs during single column gas chromatography (1DGC), making the detection and identification of character-impact odorants challenging. Therefore, comprehensive two-dimensional gas chromatography (GCxGC) combined with time-of-flight mass spectrometry (TOFMS) was used to resolve and identify compounds eluting in the odour active regions. The methodology was developed in a case study on coriander (Coriandrum sativum) and wild coriander (Eryngium foetidum) leaf essential oils. During GC-O analysis of these samples it was recognised that odour active regions frequently coincide with several co-eluting compounds. To address this, a heart-cut multidimensional gas chromatography-olfactometry (MDGC-O) instrument was developed to resolve these 'co-eluting odour clusters' and determine the compound(s) responsible for the odour perception. The 'spicy' character of hops is considered to be a desirable attribute in beer associated with 'noble hop aroma'. However, the compounds responsible have yet to be adequately elucidated. This character was investigated using a commercial 'Spicy' fraction of hop essential oil, selectively enriched for monoterpene and sesquiterpene alcohols. The odour active compounds in (i) the spicy fractions and (ii) the whole essential oils of four different hop varieties were compared using the presented methodology. A compound with an intense 'woody, cedarwood' odour was determined to be a potent, character-impact odorant in all samples. This odour coincided with a complex region of the chromatogram where up to thirteen compounds were co-eluting. The peak responsible for this odour was determined by (i) correlation of peak areas with odour potency (Charm) values and (ii) MDGC-O. The compound was tentatively identified by GCxGC-TOFMS as 14-hydroxy-β-caryophyllene, which has not previously been reported as an odorant in hop essential oil. It was concluded that this compound and other 'woody, cedarwood' odorants contributed to the 'spicy' character of the investigated hop samples. Compounds previously associated with noble hop aroma, notably caryophyllene oxide, humulene epoxides I and II, and humulenol II, did not contribute to the odour character of the hop samples. Other potent odorants that were identified in the whole essential oil and spicy fractions of hops were: geraniol, linalool, β-ionone, eugenol, isovaleric acid, and β-damascenone. While myrcene was a moderately potent odorant in the whole hop essential oil samples, the abundant sesquiterpene hydrocarbons α-humulene, β-caryophyllene and β-farnesene did not significantly contribute to the odour character.

Master of Science
Food Science Institute -- Human Nutrition
Koushik Adhikari
A significant increase in the number of products carried in supermarkets has lead manufacturers to use food color as a way to differentiate their products from competitor’s products or as a form of communication. This report’s overall objective was to review the impact of color on sensory properties of foods and beverages and help product developers understand the multiple sensory properties within a food or beverage that may potentially change by manipulating color. The effect of color on flavor or odor identification, basic taste perception, flavor or odor intensity, quality and refreshment, and consumer acceptance has been extensively researched. Research to date has shown inconsistent findings, although key themes are consistent. Some colors are more appropriate for certain foods and beverages, and product color can be directly linked to palatability. Color cues can be used for flavor identification within a food or beverage, and the presence of certain colors evoke flavor associations within a product. Perceived intensities of basic taste or flavor attributes have increased or decreased merely with color addition. Consumers use color cues to determine quality, therefore color can ultimately affect product acceptance.

Thesis (PhD)--Stellenbosch University, 2005.
ENGLISH ABSTRACT: A number of relevant brewing industry issues associated with malt quality were examined. These included beer foam quality, premature flocculation of yeast during fermentation and antimicrobial factors in malt. The cause of poor foam at a brewery relative to other similar breweries was identified as being related to the boiling temperature during wort preparation and the associated conformational changes of the abundant foam protein lipid transfer protein 1 (LTPl). The temperature range of 96 to 102°C was revealed to be critical. At the higher temperature the denaturation of LTP 1 was more extensive and its effectiveness as a foam protein was reduced. In addition, it was shown that the prominent role of LTPI with respect to foam was as a lipid binding protein, forming a lipid sink and protecting foam from lipid damage. The occurrence of malt associated premature yeast flocculation (PYF) during fermentation was induced in malt by the addition of extra-cellular fungal enzymes to the malt husk or by micro-malting barley in the presence of fungi. In addition, treating malt husk with commercial xylanase or adding commercial arabinoxylan to the fermentation also impacted on yeast flocculation. It was proposed that a range of molecular weight arabinoxylans formed by the enzymatic breakdown of the major barley husk component (arabinoxylan) resulted in PYF. Antimicrobial activity against brewing yeast (Saccharomyces cerevisiae), other fungi and bacteria was found in barley, malt and malt derived wort trub. Wort trub is the non-specific precipitate of protein, polyphenols and lipids formed during wort boiling and which is, to some extend, carried over in the wort to the fermentation. Antimicrobial activity appeared to increase during malting. The growth of brewery collected yeast was inhibited in the presence of brewery production wort when compared to the same wort filtered to remove the trub. Brewery yeast was found to be more sensitive to inhibition than laboratory propagated yeast of the same strain. Different strains of S. cerevisiae were also found to differ in their sensitivity to inhibition. Investigation revealed that the activity originated from the inside of the barley grain and impacted on yeast sugar uptake. However, there was no direct correlation detected between levels of antimicrobial activity in malt and fermentation performance. At high concentrations the factors were microcidal causing cell lysis. Partial characterisation of an antimicrobial extract from malt revealed the presence of a factor between 5 and 14 kDa, containing a cationic peptide component. The optimum pH stability was ±5 when it was also most cationic. The factor easily and irreversibly lost activity at extreme pH and when exposed to certain reagents but was heat resistant in accordance with its survival in wort trub. Preliminary results showed the presence of LTP1 associated with other peptides in the active cationic fraction from the one malt tested. The occurrence of malt related PYF and malt antimicrobial factors are associated with microbial contamination of the grain. The fungi generating the PYF factors from the barley husk while the barley's defence mechanism generates antimicrobial factors to cope with the pathogenic effect of the fungi. In addition there is a potential link between the foam protein LTP 1 and malt antimicrobial activity as LTP 1 or LTP 1 in association with another component(s) is potentially antimicrobial.
AFRIKAANSE OPSOMMING: 'n Aantal problematiese areas in die broubedryf, wat met mout geassosieer word, is ondersoek, naamlik bierskuimkwaliteit, voortydige flokkulering van gis tydens fermentasie en die invloed van antimikrobiese faktore in mout. Die oorsaak van swak bierskuim by 'n spesifieke brouery relatief tot ander soortgelyke brouerye was geidentifiseer as die moutekstrakkookpunt tydens moutekstrakbereiding. Tydens hierdie proses ondergaan dieskuimprotein, lipiedoordrag proteien 1 (lipid transfer protein 1, LTPI), 'n konformasieverandering. Die temperature tussen 96 to 102°C was kritiek t.o.v. ideale konformasieverandering vir skuimaktiwiteit. Denaturering van LTPI het by hoër temperature plaasgevind wat die skuimproteien se aktiwitiet verminder het. Daar is ook bewys dat LTPI 'n verdere rol in bierskuim speel aangesien dit 'n lipiedbindingsproteien is wat die skuimnegatiewe lipiede verwyder. Die voorkoms van moutgeassosieerde voortydige flokkulering van gis (PYF) tydens fermentasie is op twee maniere in mout geinduseer, naamlik: • deur die toevoeging van ekstrasellulêre swamensieme tot die moutdop • deur mikrovermouting van gars in die teenwoordigheid van swamme. Die behandeling van die moutdop met kommersiele xilanase of die toevoeging van kommersiele arabinoxilaan by fermentasies het ook die flokkulering van gis beinvloed. Die hipotese was dat PYF veroorsaak is deur 'n reeks arabinoxilane met verskillende molekulêre massas wat gevorm het tydens die ensimatiese afbraakproses van die primere moutdopkomponent (arabinoxilaan). Antimikrobiese aktiwiteit teenoor brouersgis (Saccharomyces cerevisiae), ander swamme en bakterie was teenwoordig in gars, mout en moutekstrakpresipitaat. Die presipitaat bestaan uit nie-spesifieke presipitate van proteien, polifenole en lipiede wat gedeeltelik in die gekookte moutekstrak agterbly. Daar is gevind dat antimikrobiese aktiwiteit tydens vermouting toe geneem het. Die groeiproses van brouersgis, gekollekteer by 'n brouery, was geinhibeer deur die teenwoordigheid van brouery-geproduseerde moutekstrak in vergelyking met dieselfde moutekstrak wat gefiltreer was om die presipitaat te verwyder. Die brouersgis was meer sensitief heens inhibisie in vergeleke met dieselfde gisstam wat opgegroei is in die laboratorium. Verskillende S. cerevisiae stamme het ook verskille in sensitiwiteit getoon t.o.v. the antimikrobiese komponente in die moutekstrakte. 'n Verdere ondersoek het getoon dat die oorprong van die inhiberende aktiwiteit die interne dele van die gars is, asook dat dit die gissuikeropname beinvloed. Daar was egter geen direkte verband tussen antimikrobiese aktiwiteit in mout en fermentasie effektiwiteit, soos gemeet onder laboratorium toestande, nie. Hoë konsentrasies van die faktore het egter gelei tot seldood weens sellise. 'n Kationiese peptiedbevattende fraksie tussen 5 en 14 kDa en 'n optimale pH stabliliteit van 5 is gevind deur gedeeltelike karakterisering van 'n antimikrobiese moutekstrak. Die aktiewe fraksie se aktiwiteit is onomkeerbaar vernietig by ekstreme pH en blootstelling aan sekere reagense. Die aktiewe verbinding(s) is egter hittebestand en resultate het getoon dat hierdie aktiwiteit die brouproses oorleef as deel van die moutektrakpresipitaat. Voorlopige resultate van die een mout wat getoets is het die teenwoordigheid van LTP 1 getoon, asook die moontlike assosiasie met ander peptiede of kleiner komponente in die aktiewe kationiese fraksie. Die voorkoms van moutgeassosieerde PYF en antimikrobiese faktore in mout word met die mikrobiologiese kontaminasie van gars verbind. Swamme produseer die PYF faktore vanuit die moutdopkomponente, terwyl die plant weer antimikrobiese faktore produseer as deel van 'n beskermingsmeganisme teen die patogene effek van die swamme. Daar is ook 'n potensieele verwantskap tussen bierskuimproteien LTP 1 en antimikrobiese faktore in mout, aangesien LTPI ofLTPl tesame met 'n ander verbinding(s) moontlik antimikrobies is.

This study was conducted to determine the effect of heating methods (conventional and microwave), heating temperatures, and refrigerated storage on the flavor deterioration in precooked chicken parts. Chicken breasts and legs were evaluated by chemical analyses and sensory evaluation. Data was analyzed by Fisher's least significant difference (LSD) and Duncan's test. Results of the thiobarbituric acid test (TBA) indicated that heating temperature, regardless of heating method had a significant influence on oxidative deterioration. When the legs were heated for a longer time at a lower temperature, the TBA values significantly increased indicating heightened warmed-over flavor (WOF). Two-day refrigerated storage had no measurable influence on the TBA numbers. The legs generally had a higher degree of lipid oxidation reflected by higher TBA values. Heating method and 2-day refrigerated storage did not have a significant effect on the nonheme iron content of breasts or legs. The effects of heating temperature were inconsistent for the legs and breasts which was attributed to the different initial iron content of the legs, and the release of nonheme iron during the initial processing of the legs. The nonheme iron values of the legs were greater relative to the breasts. Heating and storage in general increased the area of peak 3 in legs, but had no effect on the breasts. A significant increase in the hexanal (peak 8) content of legs occurred upon 2-day storage, but not for breasts. Peak 7 significantly decreased when the breasts were heated, stored, and reheated. This was not the case for the legs. Sensory panelists could not differentiate between heating methods or temperatures for either part.
Master of Science

The flora of Aotearoa/ New Zealand has evolved in association with birds and lizards as the dominant frugivores and seed dispersers. There is a wide range of ripe fruit colours within the native fleshy-fruited plants spanning the visible light spectrum from red to violet, with the notable exception of green. The evolution of fleshy-fruit and fruiting related trait, may be a result of the selection pressures exerted by different frugivore guilds. This study was conducted to ascertain if endemic diurnal lizards, Oligosoma species (Scincidae: Lacertilia), display features associated with visual based foraging, colour sensitivity and colour preferences, which are necessary conditions to infer a co-evolutionary mutualism between fleshy-fruited plant species and lizards as seed dispersers, which may have influenced the evolution of fruit colour. Many lizards have exceptional colour vision, with the ability to see a wide range of the visual light spectrum from short wave ultra violet to long wave red. They are able to discriminate all aspects of colour: hue, brightness and saturation. Fruit colour within Coprosma (Rubiaceae), is extremely variable, between and within species. The study of fruit colour preferences within this genus and particularly within species with polymorphic fruit colour provides a valuable comparison of frugivore preference to fruit with little inter and intraspecific variation, therefore minimising potentially confounding factors due to phylogeny. Fruit-colour choice experiments were conducted offering fruit from two colour categories based on postulated frugivore preferences; red and red orange fruit has been associated with avian frugivores whilst white and pale fruit has been associated with lizard frugivory in New Zealand. Experiments were conducted both ex-situ, in environmentally controlled laboratories and in-situ at Macraes Flat, Otago. Pilot trials indicated that the background colour on which fruit were presented was important in fruit choice and consequentially, all fruit were offered on a background which provided contrast to both fruit colour categories. The laboratory trials showed some weak evidence for a preference of white and pale blue fruit however, in-situ trials showed a strong preference for white over red fruit. Field studies were conducted to ascertain the composition of fleshy-fruit in the diets of lizards and the results were consistent with those expected for a generalist omnivore; many of the small fruits available to lizards were consumed however, the results indicated that plant abundance does not adequately explain fruit consumption at this field site. A preference index showed that white and pale fruited plants, Melicytus alpinus and Coprosma spp., were preferred over more abundant orange and red fruited plants. Fruit odour was investigated to determine if fruit choice was mediated primarily by visual cues as opposed to odour cues. Fruit choice trials with the fruit concealed from view indicated that fruit choice was based primarily on visual cues in Oligosoma skinks. It is concluded that lizards demonstrate the necessary conditions to infer that as frugivores, they may have influenced the evolution of fruit colour and that within the open habitats of Aotearoa/ New Zealand, the shrubs, particularly the divaricate shrubs may have provided sufficient environmental conditions to establish a mutualism between plants and lizards resulting in the evolution of small, white and other low chroma fruits.

Thesis (MSc)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: ~-Glucosidases constitute a major group of biologically important enzymes that catalyze the hydrolysis of glycosidic linkages in ~-glucosides, as well as in glycosides that contain only carbohydrate residues, e.g. cellobiose. These enzymes occur in all living kingdoms and perform a variety of functions in organisms ranging from bacteria to highly evolved mammals. Three different types of ~-glucosidases are found in humans, each with its own function: glucocerebrosidase (a deficiency causes Gaucher disease), lactase-phlorizin hydrolase (a deficiency results in lactose intolerance) and cytosolic ~-glucosidase (responsible for the hydrolysis of ~- glucosides ingested with foods of plant and animal origin). In plants, the functions of ~-glucosidases include pigment metabolism, biomass conversion and cyanogenesis, a function it shares with insect ~-glucosidases. Microbial ~-glucosidases, as part of the cellulase enzyme system that is responsible for the hydrolysis of cellobiose and short-chain oligosaccharides into glucose, playa role in the conversion of cellulosic biomass to liquid fuel. These microbial ~-glucosidases also playa very important role in the enhancement of fruit and wine aromas through the liberation of monoterpenols. Monoterpenols play an invaluable role in the flavor and aroma of grapes and wine, and are present as free, volatile and odorous molecules, as well as flavorless, non-volatile glycosidic complexes. These complexes most often occur as 6-0-~-Dxvlopyranosyl- B-Dcqlucopyranosides, 6-0-~-D-glucopyranosyl-~-D-glucopyranosides, 6-0-a-L-arabinofuranosyl-~-D-glucopyranosides, 6-0-a-L-rhamnopyranosyl-~-Dglucopyranosides, or 6-0-~-D-apiofuranosyl-~-D-glucopyranosides of mainly linalool, geraniol, nerol, a-terpineol and hotrienol. Two mechanisms exist for the release of monoterpenes from glycosidically bound non-volatile precursors: acid hydrolysis and enzymatic hydrolysis. As high temperature acid hydrolysis causes a rearrangement of the monoterpene aglycones, the focus has shifted towards the more efficient enzymatic hydrolysis that does not result in modifications of the intrinsic aromatic character of the wine. The endogenous ~-glucosidases of grapes (Vitis vinifera), as well as of the wine yeast Saccharomyces cerevisiae, exhibit very low activity towards the glycoside precursors, and thus the focus has increasingly fallen on the addition of exogenous ~-glucosidases to enhance wine flavor. Fungal, bacterial and some yeast ~- glucosidases have been indicated as effective aroma liberators, but these enzymes are not always suitable for use under the harsh conditions that prevail during winemaking (i.e. low pH, low temperatures, and high ethanol and glucose concentrations). The limited enzyme activities of the abovementioned microorganisms have resulted in a search among non-Saccharomyces yeasts for ~- glucosidases that can withstand these conditions. The ~-glucosidase activities of 20 wine-associated non-Saccharomyces yeasts were quantified, characterized and assessed to determine the efficiency with which they could liberate monoterpenols from their terpenyl-glycosides. The Debaryomyces pseudopolymorphus l3-glucosidase from intracellular crude cell extracts exhibited the most suitable combination of properties in terms of functionality at wine pH, resistance to wine-associated inhibitory compounds (glucose, ethanol and sulfur dioxide), high substrate affinity and large aglycone-substrate recognition. This yeast strain was also used, in conjunction with S. cerevisiae VIN13, for the small-scale fermentation of Chardonnay juice. The results indicated that the l3-glucosidase of D. pseudopolymorphus had definite potential as a wine aroma-enhancing enzyme, as the concentrations of free terpenols (nerol, geraniol and citronellol) were significantly increased during fermentation. Future experimental work would include an in-depth study of the kinetic characteristics of the l3-glucosidases (both cytosolic and cell-associated) exhibiting the highest terpenol-liberating activity under winemaking conditions. The next step would then be the cloning and expression of the most efficient l3-glucosidase gene in a commercial wine yeast. Such a recombinant wine yeast would release grapederived aroma compounds from their non-volatile precursors during single culture fermentations, thereby increasing the sensorial quality of wine.
AFRIKAANSE OPSOMMING: I3-Glukosidases vorm deel van 'n groot groep biologies belangrike ensieme wat die hidrolise van glikosidiese bindings binne l3-glukosiede,sowel as binne glikosiede wat slegs uit koolhidraatresidue bestaan, soos bv. sellobiose, kataliseer. Hierdie ensieme kom in alle koningkryke van lewende organismes voor en verrig 'n wye verskeidenheid funksies binne organismes wat wissel van bakterieë tot hoogs ontwikkelde soogdiere. Drie verskillende tipes l3-glukosidases,elk met sy eie funksie, kom in mense voor: glukoserebrosidase ('n gebrek hieraan lei tot Gaucher-siekte), laktaseflorizinhidrolase ('n gebrek hieraan gee aanleiding tot laktose-intoleransie) en sitosol l3-glukosidase (verantwoordelik vir die hidrolise van l3-glukosiede wat saam met voedsel van plant en dier oorsprong ingeneem word). Die funksies van 13- glukosidase binne plante sluit in pigmentmetabolisme, biomassa-omsetting en sianogenese, wat ook 'n funksie van insek l3-glukosidases is. Mikrobiese 13- glukosidases, as deel van die sellulase-ensiemsisteem wat verantwoordelik vir die hidrolise van sellobiose en kortketting-oligosakkariede na glukose is, speel 'n rol in die omsetting van sellulosebiomassa na brandstof. Hierdie mikrobiese 13- glukosidases speelook 'n baie belangrike rol in die verbetering van vrugte- en wynaroma deur die vrystelling van monoterpenole. Monoterpenole speel 'n belangrike rol in die geur en aroma van druiwe en wyn, en kom voor as vry, vlugtige en aromatiese molekules, asook geurlose, nie-vlugtige glikosidies-gebonde komplekse. Hierdie komplekse is meestal in die vorm van 6-0- I3-D-xilopiranosiel-I3-D-glukopiranosiede, 6-0-a-L-arabinofuranosiel-I3-D-glukopiranosiede, 6-0-I3-D-glukopiranosiel-I3-D-glukopiranosiede, 6-0-a-L-ramnopiranosiel- I3-D-glukopiranosiede,of 6-0-I3-D-apiofuranosiel-I3-D-glukopiranosiedevan hoofsaaklik linalool, geraniol, nerol, a-terpineol en hotrienol. Monoterpenole kan op een van twee maniere van hul suikermolekules vrygestel word: suurhidrolise of ensimatiese hidrolise. Die hoë temperature waarby suurhidrolise plaasvind veroorsaak 'n herrangskikking van die monoterpeen aglikone, en die fokus het gevolglik verskuif na die meer effektiewe ensimatiese hidrolise wat nie verandering van die intrinsieke aromatiese karakter van die wyn tot gevolg het nie. Die endogene l3-glukosidases van druiwe (Vitis vinifera) en die wyngis Saccharomyces cere visiae , toon baie lae aktiwiteit ten opsigte van die aromatiese voorlopers, en dus word daar toenemend op die toevoeging van eksogene 13- glukosidases tot die wyn gefokus om meer geur vry te stel. Daar is bevind dat 13- glukosidases van fungiese, bakteriële en gis oorsprong effektiewe aromavrystelIers is, maar hierdie ensieme is nie altyd gepas vir gebruik in wyn nie, aangesien dit 'n omgewing is met 'n lae pH, lae temperatuur, en hoë etanol- en glukosekonsentrasies. Die beperkte ensiemaktiwitiet van bogenoemde mikroorganismes het gelei tot 'n soeke onder nie-Saccharomyces giste na l3-glukosidases wat in die wynomgewing kan funksioneer. Die ~-glukosidase-aktiwiteit van twintig wyn geassosieerde nie-Saccharomyces giste is gekwantifiseer en gekarakteriseer om te bepaal tot watter mate dit monoterpenole van hul terpeniel glikosiede kan vrystel. Die intrasellulêre ~- glukosidase teenwoordig in the selekstrak van Debaryomyces pseudopolymorphus, het die belowendste resultate getoon ten opsigte van funksionaliteit by wyn se pH, weerstand teen wyn geassosieerde inhibeerders (glukose, etanol en swaweidioksied), hoë substraataffiniteit en breë aglikoon-substraat herkenning. Hierdie gisras is ook in kombinasie met S. cerevisiae VIN13 gebruik vir die kleinskaalse fermentasie van Chardonnay sap. Die resultate het getoon dat die ~- glukosidase van D. pseudopolymorphus wel potensiaal het om wynaroma te verhoog, aangesien die konsentrasie van ongebonde terpenole (nerol, geraniol en citronellol) aansienlik tydens fermentasie toegeneem het. Toekomstige eksperimentele werk sluit in, onder meer, In in-diepte studie van die kinetiese eienskappe van die ~-glukosidases (beide sitesolies en sel-geassosieerd) wat die meeste terpenole onder wynrnaakkondisies vry stel, asook die klonering en uitdrukking van die enkele ~-glukosidasegeen met die hoogste aktiwiteit, in In kommersiële wyngis. Só In rekombinante wyngis sal die vrystelling van druifgebaseerde aromakomponente van hul nie-vlugtige, geurlose voorlopers tydens enkel-kultuur fermentasies teweeg bring.

As the bottled water trend continues to rise across the nation, drinking water utilities have become more concerned with ensuring consumer satisfaction of their product. Although public water supplies are safeguarded by regulations, aesthetically unappealing taste-and-odor problems have led consumers to search for alternative water sources, such as bottled water or tap water processed by point-of-use filters. Consequently, taste-and-odor monitoring has become important to the drinking water industry. Because many utilities use chlorine to disinfect the water, chlorine odor often masks other more subtle odors that may eventually cause consumer complaints. As treated water travels from the water treatment plant to the consumer, chlorine residual diminishes and may reveal a water's naturally less-pleasing odors. Consequently, odor monitoring at the water treatment plant, where chlorine concentrations are at a peak, may not identify potential displeasing smells. Proper evaluation of these odor-causing substances requires that the chlorine odor first be eliminated before evaluating any remaining odors. Dechlorinating agents can remove chlorine, but some will produce other unwanted odors or even remove certain odorous compounds. This research describes the efficiency of several of these agents (ascorbic acid, hydrogen peroxide, oxalic acid, sodium nitrite, and sodium thiosulfate) in dechlorinating chlorinated solutions of the earthy-smelling compound geosmin and musty-smelling MIB. Interfering odors in reusable containers pose another problem in drinking water odor analysis. The most common odor-analysis methods (TON and FPA) involve the use of glass flasks, which often either develop chalky odors or have persistent lingering odors from previous evaluations. Furthermore the glass flasks break easily and are difficult to clean. This research also evaluates the suitability of four types of disposable plastic containers for odor analyses.
Master of Science

Copies of author's previously published articles inserted. Bibliography: leaves 121-144. This study investigates the site of biosynthesis of flavour compounds in the grapevine. Most of the secondary metabolites, including flavour compounds, are glycosylated and stored in plant tissues as glycosides. The chemical properties of these compounds, especially their water solubility, suggests that glycosides might be forms of translocated secondary metabolites in plants.

Orientador: Maria Aparecida A. P. da Silva
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Para a recuperação do aroma e sabor de fruta fresca ao suco industrializado, subprodutos do processamento do suco de laranja, como óleo essencial e essências aquosa e oleosa, são normalmente reincorporados ao produto processado. A adição de cada um desses subprodutos confere ao produto final qualidade e estabilidade sensoriais distintas. O presente trabalho teve por objetivo avaliar a qualidade e estabilidade sensoriais do suco de laranja reconstituído, produzido com laranjas de variedades brasileiras e aromatizado com quatro diferentes aromas naturais de laranja, quais sejam: I - óleo essencial; II - frações destiladas de essência oleosa (oil phase); III - aroma formulado contendo frações destiladas de óleo essencial e de essência oleosa; e, IV - aroma formulado contendo frações destiladas de óleo essencial, frações destiladas de essência oleosa e de essência aquosa (water phase). Assim, esta pesquisa consistiu em quatro etapas, a saber: avaliação do impacto dos quatro aromas naturais sobre a aceitação e perfil sensorial do suco de laranja pronto para beber em condições pré-processamento térmico; avaliação da estabilidade sensorial dos aromas naturais ao processamento térmico do suco; avaliação do impacto dos aromas naturais sobre a estabilidade sensorial do suco pronto para beber durante o armazenamento da bebida e, finalmente, a identificação de compostos voláteis odoríferos presentes em um dos aromas mais estáveis - Aroma III. Quatro formulações de suco de laranja reconstituído foram elaboradas, adicionando-se os aromas I, II, III e IV, processadas e envasadas assepticamente em garrafas PET. Os perfis sensoriais, através de Análise Descritiva Quantitativa, e a aceitação das quatro formulações de suco de laranja pronto para beber foram avaliados antes e após o processamento térmico, bem como durante o armazenamento da bebida por 20, 40, 60 e 90 dias. Índices de escurecimento e teores de vitamina C foram determinados durante o armazenamento. Adicionalmente, amostras comerciais de suco de laranja pronto para beber foram avaliadas. Os dados foram analisados por ANOVA, teste de média Tukey ou t-Student, Mapa de Preferência, Análise de Componentes Principais, análise de correlação de Pearson e análise de regressão linear dos parâmetros sensoriais em função do tempo de armazenamento da bebida. O aroma III foi avaliado por cromatografia gasosa (CG), CG-olfatometria (Osme) e espectrometria de massas. Os resultados obtidos na primeira etapa da pesquisa sugeriram que a reincorporação dos compostos voláteis provenientes da essência oleosa contribuem menos para aumentar a aceitação do suco de laranja do que aqueles provenientes do óleo essencial. Em contrapartida, as amostras comerciais tiveram aceitação modesta entre os consumidores indicando que, no Brasil, os sucos de laranja comerciais podem ainda ter sua qualidade sensorial melhorada pela adição de novos aromas naturais. Na segunda etapa, a avaliação da aceitação das amostras pré e pós-processamento indicou boa estabilidade dos aromas naturais estudados ao processamento térmico. Os perfis sensoriais das formulações sugeriram que: i) a reincorporação ao suco de frações destiladas dos três subprodutos do processamento da laranja, resulta em maior estabilidade térmica do que aromas derivados apenas do óleo essencial; e, ii) a presença de voláteis provenientes da essência aquosa no aroma natural de laranja, mesmo que em proporções minoritárias, realça no suco notas de sabor de suco natural e suaviza as notas de aroma e sabor de casca de laranja. Na terceira etapa, durante o armazenamento da bebida, a formulação contendo apenas frações de essência oleosa apresentou, notadamente, menor estabilidade sensorial do que as demais formulações, contendo compostos voláteis provenientes do óleo essencial. Possivelmente essa ocorrência seja devida à presença de agentes antioxidantes naturais nas frações derivadas do óleo essencial. Adicionalmente, os resultados sugeriram que a adição ao suco de laranja de frações destiladas de óleo essencial resulta em melhor estabilidade sensorial à bebida do que a adição ao suco do óleo essencial na sua forma integral. Em todas as amostras, ao longo do período de armazenamento, ocorreu queda dos teores de vitamina C e concomitante escurecimento dos sucos. Finalmente, na última etapa, foram gerados 55 picos de odores, os quais apresentaram, predominantemente, notas de aroma associadas à laranja. Beta-mirceno, butanoato de etila, a-pineno, hexanal, citral e decanol foram os compostos voláteis de maior importância odorífera identificados. Os compostos ß-terpineol, citronelal, undecanal, acetato de a-terpenila, acetato de nerila e a-cariofileno foram identificados como compostos de alto poder odorífero e, limoneno, linalol, a-terpineol e decanal, como compostos de baixo poder odorífero
Abstract: To restore the natural orange aroma and flavor to industrialized juices, processors add natural flavorings obtained from three orange juice by-products: the cold-pressed oil, the oil phase and the water phase. The addition of each of these by-products results in juices with distinct sensory characteristics and acceptability. The present work aimed at evaluating the sensory quality and stability of reconstituted orange juice from Brazilian varieties, flavored with four different orange natural aromas, which are: I ¿ essential oil; II ¿ distilled fractions of the oil phase; III - formulated aroma containing distilled fractions of the essential oil and of the oil phase e, IV ¿ formulated aroma containing distilled fractions of the essential oil, distilled fractions of the oil phase and of the water phase. Thus the present research was divided into four stages: evaluation of the impact of four natural aromas (I, II, III, IV) on the acceptability and sensory profile of ready-todrink orange juice before thermal treatment; evaluation of the sensory stability of the natural aromas to the thermal treatment of the juice; evaluation of the natural aromas impact to the sensory stability of ready-to-drink orange juice during storage; the identification of odor volatiles compounds in one of the most stable aromas ¿ Aroma III. Four reconstituted orange juices formulations were elaborated, by adding the above mentioned flavorings (I, II, III, IV), processed and packed in PET bottles. The sensory profiles, by using Quantitative Descriptive Analysis, and the acceptability of the four ready-to-drink orange juices were evaluated before and after the processing, and also during their 20, 40, 60 and 90 day-storage. In addition, other commercial samples of ready-to-drink orange juice were included in this study. Determinations of the ascorbic acid and the browning index of formulated juices were done as well. Data were analyzed by ANOVA, Tukey or t-Student mean test, Principal Component Analysis, Preference Mapping, Pearson¿s correlation analysis and linear regression analysis of sensory parameters as a function of the storage time. The aroma III was evaluated by gas chromatography (GC), GC-olfactometry (OSME) and by mass spectrometry. The results obtained from the first research stage suggested that reintroduction of the volatiles compounds from oil phase contribute less to increase the acceptability of orange juice than those from the essential oil. On the other hand, all the commercial samples presented moderate acceptability by consumers, indicating that the commercial orange juices in Brazil may have their sensory quality improved by adding new natural aromas. In the second research stage, the evaluation of the pre and post-processing samples acceptability indicated that the studied natural aromas presented good stability to the thermal treatment. The formulations sensory profiles suggested that: i) the reintroduction of the distilled fractions of the three orange processing by-products to the juice results in higher thermal stability than that caused by the aromas derived from the essential oil; ii) the presence of volatiles from distilled fractions of the water phase in the natural orange aroma, although in very small proportions, enhances natural juice flavor and softens orange peel flavor and aroma. In the third research stage, during the drink storage the formulation containing only distilled fractions of the oil phase presented much less sensory stability than the other formulations, containing volatile compounds from the essential oil. A possible explanation for this occurrence is the presence of natural antioxidants in those fractions derived from essential oil. Further, the results suggested that the addition of distilled fractions of essential oil to orange juice provides better sensory stability to the drink than the addition of the integral essential oil. During storage all samples showed decrease in vitamin C and simultaneous browning of juices. Finally, in the last research stage, Fifty-five odor peaks were generated, which presented aroma notes associated mostly to orange. Beta-myrcene, ethyl butanoate, a-pinene, hexanal, citral and decanol were identified as the highest aroma impact compounds. The compounds ß-terpineol, citronellal, undecanal, a-terpinyl acetate, neryl acetate and a-cariophylene were identified as high odor power compounds and, limonene, linalool, a-terpineol and decanal, as low odor power compounds
Doutorado
Doutor em Tecnologia de Alimentos

Thesis (MSc)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: No single chemical constituent can be accredited with giving wine and brandy their overall aroma and flavour. The aroma and flavour of wine and brandy are rather attributed to a number of chemical constituents reacting together and it is these reactions that give the beverage its character. Certain chemicals within wine and brandy do, however, make larger contributions to the flavour. These include the esters, terpenes and volatile acids, although others also exist. Esters are a large group of volatile compounds with variable aroma and flavour characteristics, including banana-like (isoamyl acetate), apple-like (ethyl caproate) and chemical/solvent-like (ethyl acetate). Esters are produced as secondary metabolites during the conversion of sugar to ethanol and are formed when an alcohol binds with a fatty acid. Chemically, ester metabolism is well documented and understood; however, much work still needs to be done on a genetic level. The yeast strain used during fermentation is one of the most important factors contributing to the type and quantity of esters produced. This is due to differences in genetic makeup. The metabolism of esters is controlled largely on a genetic level, with numerous genes being involved. The alcohol acetyltransferase genes are involved in ester anabolism, whilst esterase genes are involved in ester catabolism. Esterases have a negative effect on the overall level of esters within an alcoholic beverage, as they are capable of reducing the number of esters and are thus capable of altering the beverage's aroma and flavour profile. The IAH1 and the TIP1 gene products are believed to encode for two such esterases. The objective of this study was to investigate the contribution of the IAH1 and TIP1 genes to the level of esters in both wine and brandy. This was accomplished by using two approaches. Firstly, the above genes were disrupted using a polymerise chain reaction (PCR)-generated disruption cassette homologous to either the IAH1 or the TIP1 gene. These cassettes were integrated into the industrial wine yeast, Saccharomyces cerevisiae strain VIN13. The integrations were verified by Southern blot analysis to produce yeasts VIN13-~IAH1 and VIN13-~TIP1; however, only a single copy of each was disrupted. Secondly, the IAH1 and the TIP1 genes were cloned from S. cerevisiae using PCR into plasmid pj between the phosphoglycerate kinase gene (PGK1) promoter and terminator, producing plasmids pJ-IOE1 and pJ-TOE1. The PGK1 promoter has previously been shown to constitutively express genes at high levels. These new constructs were then used as template for PCR to produce two overexpression cassettes, one for IAH1 and the other for TlP1. These cassettes were integrated into S. cerevisiae VIN13 and verified by Southern blot analysis to produce strains VIN13-IOE1 and VIN13-TOE1. The above yeast strains including VIN13 were used for the production of wines and base wines from Colombard must. Reverse-transcriptase (RT-PCR) confirmed that the VIN13-IOE1 and VIN13-TOE1 strains overexpressed the appropriate gene at a higher level than the control VIN13 strain. The VIN13-AIAH1 disrupted strain showed no difference in expression level to that of the control strain, whilst VIN13-ATIP1 showed lower levels of expression than that of the control strain. VIN13-IOE1 behaved as expected, with a decrease of between 30% and 60% in the total ester level in the wine and base wine respectively, a 30% decrease in the total acid level and no change in the higher alcohol level. The VIN13-AIAH1 strain showed no difference to the control wine, most likely as this strain still expressed the IAH1 gene at levels consistent with the control strain. VIN13-TOE1 behaved in an unexpected manner - instead of hydrolysing esters, it appeared to produce them. This increase in the total ester level was most noticeable during distillation, when a 20% increase took place. Another unexpected occurrence was a large decline in the total acid level, with acetic acid being the most significant contributor, decreasing by up to 78%. This is a very favourable finding, as acetic acid is a known spoilage molecule and is a cause of sluggish/stuck fermentations. VIN13-ATIP1 behaved in an opposite manner to VIN13-TOE1, with higher total acid levels and slightly decreased total ester levels, especially during distillation. Neither affected the total higher alcohol levels. Sensorially, the only significant difference in the wine samples was for the fruity flavour. A panel of judges distinguished that VIN13-TOE1 was fruitier than the other wines, with VIN13-ATIP1 being the least fruity. This study again proves the significant impact that a single gene can have on the chemical makeup of wine and brandy. The relatively simple genetic alteration of an organism can drastically change and improve not only the organoleptic properties of the organism, but its viability as well. These alterations can produce more favourable organisms with more desirable characteristics for the fermenting beverage industry to produce products of higher quality and better suitability.
AFRIKAANSE OPSOMMING: Geen chemiese komponent kan uitgesonderword as die produseerder van aroma en geur in wyn of brandewyn nie. Die aroma en geur van wyn en brandewyn word eerder toegeskryf aan die interaksie tussen 'n groot aantal chemiese komponente om aan die drank sy karakter te gee. Enkele van hierdie chemiese komponente sluit in esters, terpene en vlugtige sure, om maar 'n paar te noem. Esters is "n groot groep van vlugtige verbindings wat beskik oor 'n verskeidenheid van aroma- en geurkenmerke, soos piesangagtig (isoamielasetaat), appelagtig (etielkaproaat) en chemies/oplosmiddelagtig (etielasetaat). Esters word as sekondêre metaboliete geproduseer wanneer suikers na etanolomgeskakel word en word gevorm wanneer "n alkohol met "n vetsuur verbind. Estermetabolisme is chemies goed beskryf en verstaan, maar op "n genetiese vlak is daar nog heelwat aspekte wat nagevors moet word. Die gisras betrokke gedurende fermentasie word beskou as een van die grootse bydraes tot die tipe en die hoeveelheid esters wat geproduseer word. Dit word toegeskryf aan verskille in die genetiese saamestelling van die gisras. Ester metabolisme word grootliks deur genetiese faktore beheer en verskeie gene is betrokke. Dit is hoofsaaklik die alkoholasetieltransferasegene wat vir esterkatabolisme verantwoordelik is, terwyl die esterasegene vir esteranabolisme verantwoordelik is. Esterases het 'n negatiewe effek op die totale estervlak binne alkoholiese dranke deurdat hulle in staat is om die aantal esters drasties te verminder en sodoende die drank se aroma- en geurprofiel te verander. Daar is voorgestel dat die IAH1- en die TlP1-geen produkte is wat vir twee sulke esterases kodeer. Die doel van hierdie studie was om die IAH1- en die TIP1-gene se bydrae tot die totale estervlak in wyn en brandewyn te ondersoek. Dit is deur twee benaderings uitgevoer. Eerstens is die bogenoemde gene d.m.V. disrupsiekassette wat homoloog aan die IAH1- of die TlP1-gene was, uitgeslaan. Die disrupsiekassette is deur die polimerasekettingreaksie (PKR) geproduseer. Hierdie kassette is in die industriële wyngis, Saccharomyces cerevisiae VIN13, geïntegreer. Die integrasies is deur Southernkladanalise bevestig en het die giste VIN13-~IAH1 en VIN13-~TIP1 gelewer. Net 'n enkele kopie van elke geen is egter uitgeslaan. Tweedens is die IAH1- en TIP1-gene d.m.V. PKR vanaf S. cerevisiae binne in plasmied pJ gekloneer, tussen die fosfogliseraatkinasegeen (PGK1) se promotor en termineerder, om plasmiede pJ-IOE1 en pJ-TOE1 te produseer. Die PGK1-promotor is al tevore geïdentifiseer as "n hoë-vlak konstitutiewe uitdrukker van gene. Hierdie twee nuwe konstrukte het vervolgens gedien as templaat vir PKR om twee ooruitdrukkingskassette, een vir IAH1 en die ander vir TIP1, te produseer. Hierdie kassette is in S. cerevisiae VIN13 geïntegreer en bevestig deur Southernkladanalise. Hierdie integrasies het die giste VIN13-IOE1 en VIN13-TOE1 geproduseer. All die nuwe gisrasse, tesame met VIN13, is gebruik vir die produksie van wyne sowel as rebatwyne vanaf Colombard-mos. Omgekeerde-transkriptase polimerasekettingreaksie (OT-PKR) het bewys dat die VIN13-IOE1 en VIN13-TOE1 rasse die geskikte geen ooruitgedruk het, met hoêr vlakke as van die kontrole VIN13-ras. Dit het ook aangedui dat die VIN13-i\IAH1-ras, waarvan die geen uitgeslaan was, geen verskil in uitdrukking gehad het in vergelyking met die kontroleras nie, terwyl VIN13-i\TIP1 'n lae uitdrukkingsvlak getoon het. VIN13-IOE1 het teen verwagting opgetree, met 'n afname van tussen 30% en 60% in die totale estervlak in beide die wyne en rebatwyne. 'n Afname van 30% in die totale suurvlak, asook geen waarneembare verskil in die hoêr alkoholvlak, in vergelyking met die kontroleras, is ook opgemerk. Die VIN13-i\IAH1-ras het glad nie van die kontroleras verskil nie, heel waarskynlik omdat hierdie ras die IAH1-geen teen dieselfde vlak as die kontroleras kon uitdruk. Die VIN13-TOE1-ras het teen verwagting opgetree deurdat dit esters geproduseer het i.p.v. om esters te hidroliseer. Hierdie toename in die totale estervlak is die meeste waarneembaar tydens distillasie, met tot 'n 20% toename. Nog 'n onverwagte effek was die groot afname in die totale suurvlak. met asynsuur wat die betekenisvolste bydrae gelewer het deurdat dit 'n afname van tot 78% getoon het. Hierdie bevinding is baie voordelig, aangesien asynsuur, 'n bekende bederfmolekuul, veral vir slepende/gestaakte fermentasies verantwoordelik is. VIN13-i\TIP1 het op die teenoorgestelde wyse opgetree as VIN13-TOE1, met 'n hoêr totale suurvlak en 'n klein afname in die totale estervlak. Weereens is dit meer gedurende distillasie waargeneem. Beide rasse het egter geen effek op die hoêr alkoholvlak gehad nie. Die proepaneel het, met betrekking tot die vrugtige geur, een betekenisvolle geurverskil tussen die wyne gevind. VIN13-TOE1 was meer vrugtig as al die ander wyne en VIN13-i\TIP1 was die minste vrugtig. Die studie het weereens bewys dat 'n enkele geen 'n betekenisvolle effek op die chemiese samestelling van wyn en brandewyn kan hê. Die relatief eenvoudige genetiese verandering van 'n organisme kan die organoleptiese eienskappe asook die lewensvatbaarheid van "n organisme, drasties verander en verbeter.

Thesis (MScAgric) -- Stellenbosch University, 2005.
ENGLISH ABSTRACT: Winemakers or producers are under constant pressure to reduce the operational costs for the production of wine. The reason for this being threefold: Firstly, the number of cellars and estates locally, and internationally, has grown immensely. Thus, the competition on both the national and international front has put producers under pressure to reduce their production cost in order to survive the explosion of brand possibilities on the consumer's horizons. Secondly, the exchange rate has been one of the most unpredictable variables which highlight the importance of scenario planning and sufficient financial planning in order to overcome significant exchange rate fluctuations which may cause financial strain for the business. Thirdly, the benefits of using expensive oak barrels for the maturation of premium quality wines are undisputable. These benefits include the clarification and decarbonation of wines, decrease in the astringency of tannins ("softening of tannins"), the evolution of colour, providing complementary oak aromas which increase the complexity and finesse of these wines and stabilising the colloid structure of the maturing wine. The greatest disadvantages remain nevertheless that it is a costly and labour intensive operation. Oak is an essential part of the flavour profile of many premium quality wines, and there is still a growing market demand for these wines. The use of oak barrels for the maturation of premium red wines, incorporates a specific flavour dimension to the wine (and adding value), has been the traditional way of storing wines. Well known cellars and Estates all over the world have build remarkable profiles and identities for their brands. To alter any principles regarding the use of oak will alter the style of the wines and will beyond any doubt influence their brand image negatively. Chapter 1 gives an introduction and the main aims of the study. The phenolic composition of grapes and oak are a complex mixture of different molecules which are discussed in Chapter 2. These include those responsible for the colour (anthocyanins), taste (mainly the tannins) and aroma of the wine. The composition of the oak barrel can be influenced by its origin, seasoning of the oak, toasting of the staves, age of the barrel etc. These factors all affect the chemical composition of the oak (lactones, volatile phenols, carbohydrate volatiles, hydrolysable tannins etc.) and ultimately, the wine. The chemical reactions taking place in wine during ageing are also complex, which makes maturation and research of wine in oak a complex business. The challenge, thus, developed to sustain the flavour profiles (oak attributes) and to reduce the operational costs, without influencing the identity or profile of the brand negatively. The use of oak derived products like chips, dust, blocks, staves, balls and even extracts was proposed, although it is considered by-products of the cooperage profession. Some of the major disadvantages of the use of oak derived products still remain the limited control over the production process. This may lead to inconsistency in the quality of these products. Nevertheless, the use of oak derived products and the availability of these products have grown significantly and with it a need for research on this field. Chapter 3 address the results obtained from the maturation of Pinotage, which is uniquely South African, and Shiraz wines, in different oak type barrels (French vs. American vs. Russian), as well as treatments with various oak derived products, and the influence of these oak products on the evolution of colour, phenolic development and quality of the wines during ageing. The results obtained in this project correlated with findings in the literature. The colour density, percentage of red pigment colour and S02 resistant pigments increased, especially in the first three to six months during ageing in barrels as a result of ellagic tannin extraction from the barrels and polymerisation reactions, but decreased later as maturation progresses as a result of precipitation. In some cases the use of oak increased the colour density significantly with almost 40%. The colour density, total red pigment colour and total phenolic composition decreased during bottle maturation as a result of polymerisation. No significant colour differences between the barrel types could, however, be detected. The use of oak derived products showed the same tendencies for all colour dimensions, although no significant differences could be detected between the treatments. The most significant difference was that new oak barrels contributed more to the development of colour compared to the oak treatments. The Gelatine index gives an indication of the degree of polymerisation of tannins; higher values will indicate tannins which are highly reactive and will cause an astringent mouth feel. The values should decrease as maturation progresses and tannins polymerise. Little differences between barrel types (French vs. American vs. Russian) were found in the one Shiraz, but in the two Pintage wines the index was the lowest in the wines matured in French oak after 36 months bottle ageing. Sensorial tests indicated little quality differences after 36 months between the different oak types The American oak barrels had, in general, a more "oaky bouquet", even after 36 months in the bottle. Pinotage matured with different alternative oak products showed that chips added to barrels tended to give a higher oak aroma, with a lower fruit compared to the other treatments. The same wine matured in new barrels, as expected, also had a very high oak aroma compared to the same wine matured in older barrels. This led to a higher fruit perception in the latter wines. Lees contact is a practice more commonly used in the production of white wines, but may be a dangerous practice in the production of red wines. Chapter 4 reports on the effect of lees contact during ageing of red wine on the micro flora and colour after 12 month maturation. No significant differences in microbial analysis were detected during of barrel maturation between the wines matured in the lees and the filtered wines for acetic acid, yeast and lactic acid bacteria. The initial pH differences during cold maceration and fermentation, however, did influence these numbers, with higher numbers being observed at higher pH values. However, colour differences could be detected. The concentration of yellow brown pigments (measured at 420 nm) was lower in the lees matured wines than in the filtered· wines which underwent malolactic fermentation in the barrel. Other colour differences that could be detected were higher colour density and total red pigment colour in wines as a result of longer skin contact (due to slower alcoholic fermentation rate). Thus, manipulation of the skins during alcoholic fermentation, the use of barrels and/or oak derived products in various stages of vinification and maturation of wines and additional practices as maturation on lees may be thus be used to set a certain style of wine which meet a specific market demand, trend or style. Chapter 5 summarises the results obtained and future research to be done on wood and wine. This study, however, clearly showed that the origin and oak type does not influence the colour as much as the aroma and taste of red wine under South African conditions.
AFRIKAANSE OPSOMMING; Wynmakers of produsente word onder gedurige druk geplaas om die produksiekoste van wyn te verlaag. Die redes hiervoor is drieledig: Eerstens het die getal kelders en landgoedere op nasionale en internasionale vlak geweldig toegeneem. Dus, die kompetisie op beide nasionale en internasionale gebied plaas produsente onder druk om die produksie koste van die wyn te verminder om sodoende finansieel die ontploffing van nuwe moontlike wyne op die horison van die verbruiker te oorleef. Tweedens, die wisselkoers was altyd een van die meer onvoorspelbare veranderlikes wat die belangrikheid van scenario-beplanning en weldeurdagte finansiele beplanning beklemtoon om sodoende groat veranderinge in die wisselkoers, wat moontlike finansiele druk in die besigheid mag veroorsaak, te oorkom. Derdens, een van die grootste uitgawes in die produksie proses van is die verouderingskomponent van kwaliteitswyn. Die voordele van die gebruik van eikehout vate in die verouderingsproses van rooiwyne is welbekend. Hierdie voordele sluit in die suiwering van die wyn in terme van soliede partikels , dekarbonisering (C02-ontgasting}, afname in die vrank smaak ("sagtheid van die tanniene), die ontwikkeling van die kleur van die wyn, toevoeging van komplementere hout boeketstowwe wat bydrae tot die kompleksiteit van die wyn, asook die stabilisering van die kollo"idale struktuur van die wyn. Die grootste nadeel bly, nieteenstaande, die geweldige koste verbonde aan vate, asook die hantering en onderhoud daarvan. Eike hout verwante boeketstowwe is 'n onmisbare komponent van die aroma profiel van baie kwaliteitswyne. Daar is 'n groeiende mark vir hierdie tipe wyne. Die gebruik van eikehout vate vir die veroudering van kwaliteitswyne, behalwe die bydrae van belangrike geurstowwe (een waarde), was nog altyd 'n tradisionele stap in die proses. Beroemde kelders reg oor die wereld het uitmuntende mark identiteite vir hulle self geskep, asook 'n "spesifieke identiteit" vir hulle wyn. Om enige beginsels aangaande die gebruik van eikehout te verander, sal sander twyfel die wynstyl verander en moontlik 'n negatiewe effek op die kelder se identiteit he. Hoofstuk 1 gee 'n inleiding en die hoof doelstellings van die studie. Die fenoliese samestelling van druiwe en eikehout bestaan uit 'n komplekse mengsel van verskillende molekules wat in Hoofstuk 2 beskryf word. Hierdie sluit in daardie verantwoordelik vir die kleur (antosianiene), die smaak (hoofsaaklik tanniene) en die aroma van die wyn. Die samestelling van die eikevat kan beinvloed deur die oorsprong, veroudering van die hout, roostering, ouderdom van die vat ens. Hierdie faktore beinvloed almal die samestelling van die houtvat (laktone, vlugtige fenole, hidroliseerbare tanniene ens.) en uiteindelik, die wyn. Die chemiese reaksies wat plaasvind tydens die veroudering van wyn is ook kompleks, wat die veroudering en navorsing van wyn in vate 'n komplekse proses kan maak. Die uitdaging, dus, het ontstaan om die organoleptiese profiel van die wyn (eikehout boeketstowwe) te behou en terselftertyd die produksiekoste van die wyn te verlaag. Die gebruik van eikehout verwante produkte soos skaafsels, blokkies, stawe en balke en selfs eikehout ekstrakte is aanbeveel, alhoewel dit gesien word as afvalprodukte van die kuiperye Een van die grootste nadele van eikehout alternatiewe produkte is egter die beperkte kwaliteitskontrole oor die produksieproses. Dit mag lei tot wisselvalligheid in die kwaliteit van hierdie produkte. Nieteenstaande het die gebruik van eike houtverwante produkte en die beskikbaarheid van hierdie produkte geweldig toegeneem en tesame daarmee die behoefte aan navorsing hieroor. Hoofstuk 3 bespreek resultate van die gebruik van verskillende eikehout tipe vate (Frans vs Russies vs Amerikaans), asook die gebruik van eikehout verwante produkte, op die kleur ontwikkeling, fenoliese samestelling en kwaliteit van Pinotage (eie aan Suid-Afrika) en Shiraz wyne gedurende vat en bottel veroudering. Die ontwikkeling van kleur het verskeie unieke dimensies en resultate wat verkry is in hierdie projek stem ooreen met literatuur. Die kleurdigtheid, persentasie rooi pigment en 802 weerstandbiedende pigmente het toegeneem met veroudering in houtvate (veral in die eerste drie tot ses maande) as gevolg van ellagitanniene wat geekstraeer word en gepolimerisasie, maar het later gedurende veroudering afgeneem as gevolg van presipitasie reaksies. In sekere gevalle het die kontak met hout die kleurdigtheid met tot 40% vermeerder. Die kleurdighteid, totale rooi pigmente en totale fenole het tydens bottelverouding afgeneem a.g.v. polimerisasie. Geen merkwaardige verskille kon egter tussen die verskillende vattipes gevind word nie. Verskille tussen die houtverwante produkte was ook klein en het diesefde tendense getoon as die vate. Nuwe vate se impak op die kleurprofiel en ontwikkeling van verouderde rooiwyne was egter meer beduidenswaardig as die gebruik van gebruikte vate en behandelings met eikehout verwante produkte. Die gelatien indeks verwys na die toestand van polimerisasie van tanniene. Hoer waardes kan verwag word in jong wyne en dui op hoogs reaktiewe tanniene. Die waarde sal afneem soos tanniene polimere vorm met veroudering en sal dus 'n veel minder vrank mondgevoel tot gevolg he. Klein verskille tussen die vat tipes (Frans vs Amerikaans vs Russies) is opgemerk in die een Shiraz, maar in die twee Pinotage wyne was die indeks die laagste in die wyne verouder in Franse eikehout na 36 maande se bottelveroudering. Sensoriese toetse het aangedui dat daar klein verskille gevind is tussen die verskillende eiketipes. Die wyn verouder in Amerikaanse eik het, in die algemeen, 'n sterker eikehoutkarakter gehad na 36 maande bottelveroudering. Wyn verouder met verskillende alternatiewe houtprodukte het aangetoon dat eikehouskaafels in vate 'n sterker eikehoutkarakter aan die wyn gegee het met 'n laer vrugtige aroma in vergelyking met die ander behandelings. Dieselfde wyn verouder in nuwe vate het oak, soos verwag, 'n sterk hout boeket gehad in vergelyking met die verouder in ouer vate. Dit het dan oak gelei dat laasgenoemde wyne 'n sterker vrug aroma gehad het. Veroudering van wit wyne op moer is 'n algemene praktyk, alhoewel dit minder toegepas word op rooiwyne as gevolg van verwante gevare. Hoofstuk 4 bespreek die effek van moerkontak op die mikrobiese en kleursamestelling van rooiwyn tydens 12 maande se houtveroudering. Geen noemenswaardige verskille is egter verkry tussen die wyne verouder op die moer en die filtreerde wyne vir asynsuur-, melksuurbateriee en gisgetalle nie. Aanvanklike pH verskille tydens koue masserasie en alkoholiese fermentasie het egter hierdie getalle beinvloed, met hoer ·getalle verkry in die hoer pH wyn. Die wyne wat appelmelksuurgisting in die vate ondergaan het en verouder is op die moer het egter 'n laer konsentrasie geelbruin pigmente (gemeet by 420 nm) as die gefiltreerde wyne. Ander kleurverskille sluit in hoer kleurdigtheid en totale rooi pigmente as gevolg van langer dopkontak (stadiger alkoholiese fermentasie). Manipulering van die doppe voor en tydens alkoholiese gisting, die gebruik van eikehoutvate of eikehoutverwante produkte, of kombinasies daarvan tydens verskillende produksie fases en ander praktyke soos moer kontak, kan dus gebruik word am 'n sekere styl wyn op markversoek daar te stel. Hoofstuk 5 som die resultate op, asook toekomstige navorsingsmoontlikhede wat op die gebied van hout en wyn gedoen kan word. Hierdie studie het egter duidelik aangedui dat die eikehout oorsprong en tipe die kleur nie so baie beinvloed soos die aroma en smaak van die wyn onder Suid-Afrikaanse kondisies nie.

Dissertation (PhD)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Brandy production is a multi-step process that involves grape harvesting, base wine fermentation, distillation, wood maturation and blending. Within each of these production process steps there are a number of factors that can influence the composition and resultant quality of the base wine, unaged and wood matured distillates. These factors include geographic and climatic features of the origin of grapes used, viticultural practices, grape maturity, grape variety, vintage variation, vinification techniques, storage of the base wine prior to distillation, distillation technique, age and origin of oak wood used for maturation and barrel toasting levels. The composition of flavour is extremely complex in wine and distilled beverages such as brandy. A multitude of compounds can take part in the formation of flavour, and it is rare that a particular compound, that is solely responsible for nuances of a specific flavour, is identified. Thus, taking brandy production factors and the nature of aroma and flavour into account, it is clear that thorough understanding of the complexities affecting the perception of quality in brandy is difficult. In commercial brandy production, standard operating procedures do not allow for the separate distillation of brandy base wines from different producers and mixing of base wines from different regions and producers thus occurs. This makes it difficult to determine whether the quality determination of the base wine is in fact an indication of the quality of the resultant distillate after the required period of wood maturation. Therefore, the aim of this study is to determine whether there is any merit in storing and distilling brandy base wines from different producers and regions separately. This was done by firstly determining the demographic and production factors that influence brandy base wine composition. Secondly, the influence of brandy base wine composition on the quality of the respective unaged potstill distillates as well as the ultimate style and quality of the threeyear old wood matured potstill distillates was determined. For this purpose, four potstills with a capacity of 2000 L each were isolated and used for commercial scale distillations of 33 and 25 brandy base wines in 1999 and 2000, respectively, at the DisteIl distillery in Worcester. The experimental outlay used in the study closely emulated Distell's standard operating procedures for commercial brandy production. Chenin blanc and Colombar are the two most popular grape varietals used in the making of brandy base wine in South Africa. Due to the complexity of the brandy production process, the first part of the study only focussed on South African young Chenin blanc wines, with a predominantly fermentation derived aroma. The concentration of iso-amyl acetate, hexyl acetate, ethyl caprylate, ethyl caprate, 2-phenethyl acetate and octanoic acid was significantly higher in wines awarded gold and silver medals and decreased significantly with subsequent decreases in quality categories. Ethyl lactate exhibited the opposite pattern. A quality predictor model based on the behaviour of 21 volatile compounds quantified in these wines had a resonable prediction accuracy when having to predict the quality of wines made in the same vintages as it had been trained on. It was significantly poorer when tested on a completely different vintage of wines to the ones it had been trained on. The number of vintages, number of wines per vintage and the number of compounds quantified for the model influence its prediction accuracy. Twenty-seven volatile compounds were quantified in 33 and 25 brandy base wines, their unaged and three year old distillates from 1999 and 2000, respectively. ANOVA and CART analysis showed that vintage, region, harvest time, choice of cultivar and yeast strain can have a significant influence on the volatile compound composition of brandy base wines, their unaged and three year old distillates. These factors as well as the volatile compound composition were also found to influence the sensory quality of these products. Base wines, unaged and three year old distillates originating from the De Dooms region, which predominantly cultivates table grapes, were of significantly lower quality than those from the remaining regions. Products made from grapes harvested early in the season were of significantly higher quality. The volatile aroma compound composition was found to differ significantly between the 1999 and 2000 base wines and distillates, irrespective of the exclusion of those samples that had undergone partial or complete malolactic fermentation. Consequently, quality indicating compounds may vary from vintage to vintage. The relationship between the quality of brandy base wines and the concentration of n-butanol, iso-amyl acetate, ethyl lactate, ethyl caprylate, octanoic- and decanoic acid was the same as that reported in young Chen in blanc wines in this study. In unaged distillates, increased levels of ethyl lactate also exert a negative influence on distillate quality. Iso-amyl acetate, hexyl acetate, ethyl caproate, ethyl caprylate, n-butanol, octanoic acid, ethyl caprate and decanoic acid showed some positive correlation, whilst iso-butanol, ethyl lactate, acetic acid, acetaldehyde and ethyl acetate showed a significant negative correlation to three-year old distillate quality. Sensory descriptive analysis on selected good, average and poor quality distillates using the South African brandy aroma wheel showed that there are small differences in profile between the good and average distillates, there were however significant differences between the good and poor quality distillate profiles throughout maturation. After three years of wood maturation, the aroma profile of poor quality distillates can be characterised by prominent herbaceous and woody aromas, which are more intense than the fruity aromas. Good quality distillates contained characteristically intense fruity aromas. Volatile compound concentration differences were noted during the course of and after three years of wood maturation and in barrels of varying ages. Distillates matured in new block barrels exhibited significant differences in volatile and wood compound composition after three years when compared to remaining barrels used. The style classification of the three-year old potstill distillate was influenced by demographic and production factors and volatile compound composition, but not by the sensory quality of the distillates. In summary, vintage, region, cultivar, harvest time and choice of yeast strain have a significant influence on the volatile composition of brandy base wines, their unaged and three year old potstill distillates, which in turn affects the sensory quality of these products. These effects cannot be viewed in isolation as they jointly exert an influence on the composition and quality of these products. From a commercial perspective, this study has provided a valuable indication as to which production and demographic factors can influence the quality and style of potstill brandy. Thus, future brandy base wine intake should, as far as possible, take place in such a manner to allow base wines originating from the same cultivar or region or harvest time or combination thereof (and to a lesser extent yeast strain) to be received simultaneously at the distillery for distillation.
AFRIKAANSE OPSOMMING: Brandewyn produksie is 'n veelvoudige proses wat die volgende insluit: pars van druiwe, basiswyn fermentasie, verstoking, houtveroudering en versnyding. Binne hierdie stappe is verskeie faktore wat 'n invloed op die samestelling en resultate van die basiswyn, onverouderde en verouderde distillaat kan hê. Hierdie faktore sluit die volgende in: geografiese ligging, klimaat toestande van die streek van herkoms, wingerdboupraktyke, graad van rypheid, druifvarieteit, wynoes variasie, wynbou tegnieke, opberging van basiswyn voor distillasie, distillasie tegnieke, ouderdom en oorsprong van akkerhout vir die veroudering, asook tot watter mate die vat gerooster is. Die samestelling van geur in wyn en gedistilleerde produkte soos brandewyn is uiters kompleks. 'n Menigte samestellings kan deel vorm van die inhoud van die geur, en dit is raar dat 'n bepaalde verbinding alleenlik verantwoordelik is vir 'n kenmerkende geur. Weens die verskeidenheid van produksie faktore, aroma en smaak is volledige kennis van brandewyn ingewikkeld en kompliseerd om te verstaan. In kommersiële brandewynproduksie, maak standaard werksprosedures nie voorsiening vir aparte distillasie van basiswyn van verskillende produsente nie, en die vermenging van basiswyn van verskillende streke en produsente kom voor. Dit maak dit moeilik om te bepaal of die kwaliteit van die basiswyn of die distillaat na die neergelegde periode van houtveroudering, in werklikheid 'n beslissende indikasie op die kwaliteit van die verouderde produk is. Daarom is een van die doele van hierdie studie om te bepaal of daar meriete in is om brandewyn basiswyn van die verskillende produsente en streke apart te berg en te verstook. Dit is gedoen deur eerstens, die effek van demografiese en produksie faktore op die samestelling van brandewyn basiswyn te bepaal. Daarna, om die invloed van brandewyn basiswynsamestelling op die kwaliteit van onderskeidelik die onverouderde distillate sowel as die uiteindelike styl en kwaliteit van die 3 jaar oue houtverouderde potketel distillate, te bepaal. Vir hierdie doel, is vier potketels met 'n kapasiteit van 2000 liters elk geïsoleer en vir kommersiële skaal distillasies van 33 en 25 brandewyn basiswyne in 1999 en 2000, ondeskeidelik, by DisteIl Distillerdery, Worcester verstook. Die eksperimentele uitleg wat in hierdie studie gebruik is, ewenaar DisteIl se standaard verstokingsprosedures vir kommersiële brandewynproduksie. Chenin blanc en Colombar is die twee mees populêre druifvarieteite vir die maak van brandewyn basiswyn in Suid-Afrika. As gevolg van die kompleksiteit van die brandewyn produksieproses, is die eerste gedeelte van die studie gefokus op die Suid-Afrikaanse jong Chenin blanc wyne, met 'n oorheersende fermentasie geur. Die konsentrasie van iso-amyl asetaat, heksiel asetaat, etiel kaprilaat, etiel kapraat, 2-phenetiel asetaat en oktanoë suur was aansienlik hoër in wyne wat met goud en silwer medaljes bekroon is en neem aansienlik af met afname in kwaliteit kategorieë. Etiel laktaat vertoon die teenoorgestelde patroon. 'n Kwaliteit voorspellersmodel, gebaseer op die gedrag van 21 vlugtige komponente was opgestel. Die model het redelike akkuraatheid getoon op wyne van dieselfde oesjaar as waarop oorspronklik opgelei. Die model se voorspellingsakkuraatheid was aansienlik swakker toe dit vergelyk getoets is met wyne van 'n nuwe oesjaar. Die hoeveelheid oesjare, hoeveelheid wyne per oesjaar en die hoeveelheid verbindings gebruik in hierdie model sal die voorspellingsakkuraatheid beïnvloed. Sewe-en-twintig vlugtige komponente was gekwantifiseer in 33 en 25 brandewyn basiswyne, die onverouderde en 3 jaar oue distillate vanaf 1999 en 2000, onderskeidelik. Variasie ontledings (ANOVA) en klassifikasie en regressie ontledings (CART) ontledings wys dat oesjaar, streek, parstyd, keuse van kultivar en gisrasse In aansienlike invloed op die vlugtige samestelling van brandewyn basiswyne asook hul onverouderde en 3 jaar distillate het. Hierdie faktore, sowel as die vlugtige verbinding samestellings, beinvloed ook bevind die sensoriese kwaliteit van hierdie produkte. Basiswyne, onverouderde en 3 jaar oue distillate wat vanuit die De Doorns streek, wat hoofsaaklik tafeldruif kultivars is, is van In swakker kwaliteit as die ander streke. Produkte wat gemaak is van druiwe wat vroeg in die seisoen gepars is, was van beter kwaliteit. Die vlugtige geurkomponentsamestellings het tussen die basiswyne en distillate van die 1999 en 2000 oesjare verskil, ongeag of party van die monsters gedeeltelike of volledige appelmelksuurgisting ondergaan het. Gevolglik, die konsentrasie van kwaliteitaanwysende komponente mag van seisoen tot seisoen verskil. Die verhouding tussen die kwaliteit van die brandewyn basiswyne en die konsentrasie van n-butanol, iso-amiel asetaat, etiel laktaat, etiel kaprilaat, oktanoë- en dekanoë suur was dieselfde soos gerapporteer oor die jong Chenin blanc wyne. In onverouderde distillate, het verhoogde vlakke van etiel laktaat In negatiewe invloed op distillaat kwaliteit veroorsaak. Iso-amiel asetaat, heksiel asetaat, etiel kaproaat, etiel kaprilaat, n-butanol, oktanoë suur, etiel kapraat en dekanoë suur In positiewe korrelasie, terwyl iso-butanol, etiel laktaat, asynsuur, asetaldehied en etiel asetaat betekenisvolle negatiewe korrelasie met 3jaar oue distillaat kwaliteit bewys. Beskrywende sensoriewe analises op geselekteerde, middelmatige en swak kwaliteit distillate (gedoen deur gebruik making van die Suid-Afrikaanse Brandewyn Aromawiel) wys dat daar klein verskille tussen die profiele van goeie en middelmatige distillate is. Daar is egter aansienlike verskille tussen goeie en swak kwaliteit distillataat profiele regdeur die drie jaar verouderingsperiode. Na 3 jaar van houtveroudering kan die geur profiel van swak kwaliteit distillate uitgeken word aan kruid- en houtagtige geure, wat meer intens as die vrugagtige geure is. Goeie kwaliteit distillate het intense vrugagtige-aroma eienskappe. Vlugtige verbinding konsentrasie verskille is waargeneem gedurende en na die 3jaar houtverouderingsperiode in vate wat van ouderdomme verskil. Distillate wat in nuwe blokkies vate verouder is, vertoon aansienlike verskille in vlugtige en houtkomponent samestellings na 3 jaar wanneer dit met die, wat in die oorblywende ouer vate verouder is, vergelyk word. Die styl klassifikasie van die 3 jaar oue potketeldistillaat was deur demografiese en produksie faktore sowel as vlugtige verbinding samestellings beïnvloed, maar nie met die sensoriese kwaliteit van die distillate nie. In opsomming, oesjaar, streek, kultivar, parstyd en keuse van gisrasse het 'n aansienlike invloed op die vlugtige komponent samestelling van die brandewyn basiswyne, onverouderde en 3 jaar oue potketel distillate, wat weer op hul beurt die sensoriese kwaliteit van die onderskeidelike produkte beïnvloed. Die effek van hierdie faktore kan nie in isolasie gemeet word nie, aangesien dit gesamentlik die kwaliteit van die produkte beïnvloed. Van 'n kommersiële perspektief het hierdie studie 'n waardevolle indikasie gelewer van hoe produksie en demografiese faktore die kwaliteit en styl van potketelbrandewyn kan beïnvloed. Daarom word voorgestel dat toekomstige brandewyn basiswyn innames, sover as moontlik, voorsiening moet maak om wyne van dieselfde kultivar, uit dieselfde streek, parsseisoen inaggeneem, of kombinasie daarvan, met 'n mindermate die gisrasse in aanmerking geneem, gelyktydig vir verstoking by die distilleerderye ontvang word sodat hierdie wyne apart van wyne met ander bogenoemde variasies verstook en verouder kan word.

Thesis (MScAgric)--Stellenbosch University, 1992.
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ENGLISH ABSTRACT: The possibility of harvesting grapes at an earlier stage of maturity, based on differences in glucose and fructose concentration which influence the sweetness of grapes, was investigated. Although differences between cultivars were found the extent was not such that a specific cultivar could be selected in order to harvest at a lower sugar concentration, but with the same sweetness. Certain characteristics of table and wine grape cultivars with respect to anatomical composition and skin penetration resistance (SPR) were also investigated in order to ascertain the extent to which grapes would resist external damage, and to what extent turgor and skin thickness contributed to SPR. Daily variances in SPR confirm that not only skin strength, but also the turgor of the grape berry contributed to SPR. Skin penetration resistance seems to be a good criterion of the extent to which cultivars would resist external damage, because it is based on the toughness of the skin and the turgor of the berry.
AFRIKAANSE OPSOMMING: Die moontlikheid van vroeer oes op grond van verskille in die glukose- en fruktosekonsentrasie wat 'n invloed op die soetheid van druiwe mag he, is ondersoek. Daar is gevind dat die verskille wat tussen cultivars voorkom nie van so 'n grootte-orde is dat 'n spesifieke cultivar geselekteer kan word ten einde by 'n laer totale suiker, maar by dieselfde soetheidsgraad, te kan oes nie. Verder is sekere eienskappe van tafel- en wyndruifcultivars t.o.v. anatomiese samestelling en doppenetrasieweerstand (DP\V) ondersoek om die moontlike weerstand teen eksterne beserings en die mate waartoe turgor en dopdikte 'n invloed daarop mag uitoefen, _vas te stel. Daaglikse variasie in DPW het bevestig dat die DPW nie alleen afhanklik is van dopsterkte nie, maar ook van die turgor van die korrel. Doppenetrasieweerstand blyk 'n goeie maatstaf te wees vir die mate waartoe cultivars weerstand hied teen sekere eksterne beserings omdat dit gebaseer is op dopsterkte en turgor van die korrel.

O café solúvel aglomerado é produto da aglomeração do café solúvel em pó. A sua produção envolve etapas de processo cujas variações térmicas modificam qualitativamente e quantitativamente a fração de compostos voláteis responsáveis pelo aroma e sabor do produto acabado. A indústria de bebidas de café considera o sabor e aroma de cereal como um defeito na produção de café solúvel aglomerado. Desta forma, este trabalho objetivou aplicar o planejamento experimental para avaliação dos parâmetros de processo da produção de café solúvel aglomerado em escala industrial. Os efeitos destes parâmetros nos componentes voláteis do café e na intensidade do gosto de cereal foram avaliados através do planejamento fracionário 24-1 com resolução IV. As variáveis independentes estudadas foram temperatura do queimador (TQ), fluxo de ar de processo (FA), temperatura da seção quente do leito (TL) e pressão de vapor (PV). Os resultados do planejamento experimental deram-se pela utilização de análise sensorial conduzida por equipe treinada para a detecção do aroma e sabor indesejado. Adicionalmente, os compostos voláteis foram extraídos pela técnica microextração em fase sólida com amostragem no headspace (HS-MFES), identificados e quantificados por cromatografia gasosa acoplada a espectrometria de massa (CG-EM). O efeito dos fatores estudados foi avaliado mediante análise de variância (ANOVA) com nível de significância de 90% e os resultados expressos por gráficos de pareto. A análise de componentes principais (ACP) foi realizada com o intuito de identificar dentre os compostos que podem conferir sabor e aroma de cereais aqueles tem a maior contribuição e quais as condições de processo ideias para evitar a formação do sabor e aroma de cereal. De acordo com ACP foi constatado que piridina, 2-metoxi-4-vinilfenol, 2,3-dimetilpirazina, 2,5-dimetilpirazina, 2,6-dimetilpirazina, 4-metiltiazol, pirazina, 2-metoxifenol, 4,5-dimetiltiazol contribuem para formação do sabor e aroma de cereal. Também indicou que a aglomeração deve ocorrer conforme TQ=215ºC, FA=250rpm, TL=120ºC e PV=1,2 x100KPa.
The agglomerated instant coffee is the product of the powder instant coffee agglomeration. Its production involves stages of processes whose thermal variations change qualitatively and quantitatively the volatile compounds fractions responsible for the aroma and flavor of the finished product. The coffee beverage industry considers the cereal like flavor and aroma as a fault in the production of the agglomerated instant coffee. In this way, this study had as the aim to apply experimental plan to evaluate the parameters of the processes of the agglomerated instant coffee production on an industrial scale. The effects of those parameters in the coffee volatile components and in the intensity of the cereal taste were evaluated through the fractional 24-1 with resolution IV. The independent variables studied were the burner temperature (BT), the process air flow (AF), the temperature of the fluidized bed hot section (LT) and the steam pressure (SP). The results of the experimental plan were made by the use of sensory analysis performed by a trained team for the detection of the undesired aroma and flavor. Additionally, the volatile compounds were extracted by solid-phase microextractiontechniquewithsampling in theheadspace (HS-SPME), identified and quantified by gas chromatography coupled to mass spectrometry (GC-MS). The effect of the factors studied was evaluated by variance analysis (ANOVA) with significance level of 90% and the results showed by Pareto charts. The principal components analysis (PCA) was made with the aim to identify, among several compounds, those that implies on more cereal flavor and aroma, those which major contribution and which ideal process conditions could be used to reduce the cereal flavor and aroma development. According to PCA, it was found that pyridine, 2-metoxi-4-vinylphenol, 2,3-dimethylpyrazine, 2,5-dimetylpyrazine, 2,6-dimethylpyrazine, 4-methyltiazol, pyrazine, 2-methoxyphenol, 4,5-dimethylthiazol contribute to the development of the cereal flavor and aroma. It was also found that the agglomeration must be according to TQ = 215°C, AF=250 rpm, LT=120°C and EPV = 1,2 x 100 KPa.

Thesis (MSc)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Wine is a complex medium. Wine aroma, flavour and colour are important quality factors, but these can be influenced by many factors, such as grape-derived compounds that exist as free volatiles and also as glycosidically bound. The chemical composition of wine is determined by factors such as grape variety, geographic position, viticulture condition, microbial ecology of the grape and the winemaking process. The varietals aroma is determined by both the volatile and the non-volatile compounds, such as monoterpenes, norisoprenoids and benzene derivatives, which are naturally present in the wine. Monoterpenes are very important in the flavour and aroma of grapes and wine. They can be found in grapes and wine either in the free, volatile and odorous form, or in the glycosidically-bound, non-volatile and non-odorous form. The ratio of glycosidically-bound compounds to free aroma compounds is very high in the Gewürztraminer, Muscat and Riesling cultivars in particular. The glycosidic bonds can be hydrolysed either by the acid method or by using enzymes. The acid method is disadvantageous because it can modify the monoterpenes, whereas enzymatic hydrolysis has the advantage of not modifying the aroma character. The enzyme method of breaking the glycosidic bonds occurs in two successive steps: initial separation of glucose from the terminal sugar by a hydrolase (a-L-arabinofuranosidase, a-L-rhamnosidase or β-apiosidase, depending on the aglycone moiety), followed by the breaking of the bond between the aglycone and glucose by β-glucosidase. The enzyme β-glucosidase can be obtained from many plant (Vitis vinifera), bacterial, yeast or fungal sources. Most of the enzymes produced by these sources are not functional under the winemaking conditions of low pH, low temperature, high glucose and high ethanol content. However, β-glucosidases from fungal origins, particularly from Aspergillus spp., are tolerant of winemaking conditions. The idea of using the β-glucosidase gene from the fungus Aspergillus kawachii (BGLA), which is linked to the cell wall and the free β-glucosidase, was to determine if anchoring the enzyme to the cell wall will increase the activity of the enzyme compared to the free enzyme. Four plasmids, pCEL 16, pCEL 24, pDLG 97 and pDLG 98, were used in this study. BGLA that was cloned into the plasmids pCEL 24 and pDLG 97 was linked to CWP2, and in pDLG 98 it was linked to AGa1 anchor domains. All the plasmids were genome-integrated and expressed in the reference strain Saccharomyces cerevisiae 303-1A. All the transformants were grown in 2% cellobiose and showed higher biomass production compared to the reference strain. β-Glucosidase activity was also assayed and transformed strain W16 showed a fourfold increase in activity compared to the reference strain. There was no significant increase in the activity of the other transformed strains, W24, W97 and W98. Enzymatic characterisation for optimum pH and temperature was done – for all strains the optimum pH was 4 and the optimum temperature was 40ºC. The recombinant strains together with the reference strain were used to make wine from Gewürztraminer grapes. The levels of numerous monoterpenes were enhanced in the resultant wines. The concentration of nerol was increased fourfold, that of citronellol twofold, and geraniol was 20% higher than in the wild type. There was also an increase in the levels of linalool and a-terpinol, but this was not significant. In wines produced with W97, W98 and W24, monoterpene levels did not show a significant difference. In future, the expression of the W16 expression cassette in an industrial wine yeast strain could be performed. In combination with the production of enzymes such as a-arabinofuranosidase, a-rhamnosidase and β-apiosidase, which are involved in the first step of enzymatic hydrolysis, this wine strain could release the bound monoterpenes and enhance the aroma of the wine.
AFRIKAANSE OPSOMMING: Wyn is ‘n komplekse medium. Wynaroma, -geur en -kleur is belangrike kwaliteitsfaktore, hoewel hierdie kwaliteite deur verskeie faktore beïnvloed kan word, soos druifafgeleide verbindings wat as vry vlugtige stowwe teenwoordig kan wees of glikosidies gebind is. Die chemiese samestelling van wyn word bepaal deur faktore soos druifvariëteit, geografiese ligging, wingerdkundige toestande, mikrobiese ekologie van die druif en die wynbereidingsproses. Die variëteitsaroma word bepaal deur vlugtige en nie-vlugtige verbindings, soos monoterpene, norisoprenoïede en benseenderivate, wat natuurlik in die wyn voorkom. Monoterpene is baie belangrik vir die geur en aroma van druiwe en wyn. Monoterpene is teenwoordig in die druiwe en wyn in vry, vlugtige en geurige, of in glikosidiesgebinde, nie-vlugtige en nie-geurige vorms. Die verhouding van glikosidiesgebonde verbindings tot vry aromaverbindings is baie hoog, veral in die Gewürztraminer-, Muscat- en Riesling-kultivars. Glikosidiese verbindings kan deur óf die suurmetode óf die ensiemmetode gehidroliseer word. Die nadeel van die suurmetode is dat dit monoterpene kan modifiseer, terwyl die ensiemmetode die voordeel het dat dit nie die aromakarakter modifiseer nie. Die ensiemmetode waarmee die glikosidiese verbinding afgebreek word, vind in twee opeenvolgende stappe plaas: aanvanklike skeiding van glukose van die terminale suiker deur ‘n hidrolase (a-L-arabinofuranosidase, a-Lramnosidase of β-apiosidase, afhangende van die aglikoongedeelte), gevolg deur die verbreking van die verbinding tussen die aglikoon en glukose deur β- glukosidase. Die β-glukosidase-ensiem kan vanaf ‘n verskeidenheid plant- (Vitis vinifera), bakterie-, gis- en swambronne verkry word. Die meerderheid van die ensieme wat deur hierdie bronne geproduseer word, is nie onder die wynbereidingstoestande van lae pH, hoë temperatuur, hoë glukose en hoë etanol funksioneel nie. β- Glukosidase vanaf ‘n swamoorsprong, veral vanaf Aspergillus-spesies, kan egter wynbereidingstoestande verdra. Die idee agter die gebruik van die β-glukosidasegeen afkomstig van die swam Aspergillus kawachii (BGLA), wat aan die selwand en die vry β-glukosidase gekoppel is, was om te bepaal of die aktiwiteit van die ensiem in vergelyking met dié van die vry ensiem verhoog sou word indien die ensiem aan die selwand geanker is. Vier plasmiede, pCEL 16, pCEL 24, pDLG 97 en pDLG 98, is in hierdie studie gebruik. BGLA, wat in die plasmiede pCEL 24 en pDLG 97 gekloneer is, is gekoppel aan CWP2, en in pDLG 98 is dit aan AGa1-ankergebiede gekoppel. Al die plasmiede is in verwysingsras Saccharomyces cerevisiae 303-1A genoomgeïntegreer en uitgedruk. Al die transformante is in 2% sellobiose gegroei en het hoër biomassaproduksie as die verwysingsras getoon. β-Glukosidaseaktiwiteit is ook geëssaieer en die getransformeerde ras W16 het ‘n viervoudige verhoging in aktiwiteit in vergelyking met die verwysingsras getoon. Daar was geen noemenswaardige verhoging in die aktiwiteit van die ander getransformeerde rasse, W24, W97 en W98, nie. Ensimatiese karakterisering vir optimum-pH en - temperatuur is gedoen – vir al die rasse was die optimum-pH 4 en die optimumtemperatuur 40ºC. Die rekombinante rasse, tesame met die verwysingsras, is gebruik om wyn met Gewürtztraminer-druiwe te maak. Die vlakke van talryke monoterpene is in die gevolglike wyne verhoog. Die konsentrasie van nerol is viervoudig verhoog, dié van sitronellol tweevoudig, en geraniol was 20% hoër as in die wilde tipe. Daar was ook ‘n verhoging in die vlakke van linaloöl en a-terpinol, maar hierdie verhoging was nie noemenswaardig nie. In wyne wat met W97, W98 en W24 gemaak is, het die monoterpeenvlakke nie ‘n noemenswaardige verskil getoon nie. In die toekoms sal die uitdrukking van die W16-uitdrukkingskasset in ‘n industriële wyngisras uitgevoer kan word. In kombinasie met die produksie van ensieme soos a-arabinofuranosidase, a-ramnosidase, β-apiosidase, wat in die eerste stap van ensimatiese hidrolise betrokke is, sal hierdie wyngisras die gebonde monoterpene kan vrylaat en die aroma van die wyn kan verbeter.

Thesis (MSc)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Monoterpene alcohols (monoterpenols) play an important role in the flavour and aroma of grapes and wine. This is especially applicable to wines of a muscat variety, but these flavour compounds are also present in other non-muscat grape varieties, where they supplement other varietal flavours and aromas. These monoterpenols can be found in grapes and wine as free, volatile and odorous molecules, as well as in flavourless, nonvolatile glycosidic complexes. These complexes most often occur as 6-0-a-L-arabinofuranosyl-p-D-glucopyranosides (vicianosides), 6-0-P-D-xylopyranosyl- P-D-gluco-pyranosides (primverosides), 6-0-P-D-glucopyranosyl-p-D-glucopyranosides (gentio-biosides ), 6-0-a-L -rhamnopyra nosyl-p-D-g lucopyra nos ides (rutinos ides), or 6-0-p-D-apiofuranosyl-p-D-glucopyranosides of mainly linalool, geraniol, nerol, a-terpineol and hotrienol. These precursors are, however, hydrolyzed only to a limited extent by endogenous glycosidases during the fermentation process, as they exhibit very low activity in wine conditions. The monoterpenols can be released from their sugar moieties by one of two methods: either an acid or an enzymatic hydrolysis. The enzymatic hydrolysis mechanism is fully understood, and the process functions in two successive steps: firstly, depending on the precursor, the glycosidic linkage is cleaved by an a-L-arabinofuranosidase, an a-L-rhamnosidase, a p-D-xylosidase, or a p-D-apiosidase. The second step involves the liberation of the monoterpene alcohol by a p-glucosidase. This enzymatic hydrolysis does not influence the intrinsic aromatic characteristics of the wine, as opposed to acid hydrolysis. As the endogenous grape glycosides of Vitis vinifera and the yeast Saccharomyces cerevisiae show very low activity towards these aromatic precursors during the handling of the juice and winemaking processes, the focus has increasingly fallen on introducing exogenous p-glucosidases to wines and juices. Genes encoding p-glucosidases and a-L-arabinofuranosidases have been cloned from various organisms, including bacteria, fungi and yeasts. However, the activities and properties of these enzymes are not always suitable for exploitation under winemaking conditions, where a low pH, low temperatures, and high ethanol and glucose concentrations prevail. A genetically engineered wine yeast strain of S. cerevisiae that expresses glycosidases that are active in these conditions would be useful in improving the flavour and aroma of wines, thereby adding to the complexity and value of the wine. Two p-glucosidase genes, BGL 1 and BGL2 from Saccharomycopsis fibufigera, were subcloned into two Escherichia coli-yeast shuttle vectors. A dominant selectable marker gene (SMR1) was also inserted onto these plasmids. These plasmids were designated pBGL 1 (containing the BGL 1 gene) and pBGL2 (containing the BGL2 gene) respectively. Introduction of the two plasmids into two strains of S. cerevisiae then followed. A laboratory strain, L1278, was transformed to confirm the effective secretion of the expressed protein. An industrial yeast strain, VIN13, was subsequently transformed by making use of the selectable marker (resistance against sulfometuron). Enzyme assays with the synthetic substrate p-nitrophenol-j3-D-glucopyranoside (pNPG) were performed to determine the activity of the j3-glucosidases over a period of days, as well as at certain temperatures and pH values. The stability of the enzymes was also investigated. These recombinant yeasts were able to degrade the pNPG efficiently. They showed promising results concerning pH optima, with a substantial amount of activity found at the pH levels as found in the wine environment. There was also a slight increase in specific activity at lower temperatures. The recombinant yeast strains were also tested in smallscale fermentations. Three wines were made, of which two were from white cultivars (Chenin blanc and GewOrtztraminer) and one from red (Pinotage). Results obtained from micro-extraction from the finished wines showed that the terpenol content did increase, although this was not the only wine component influenced. Other flavour compounds also showed increases, especially the esters. This also played a role in the flavour increase in the wine. Future work would include optimizing the available results. This would entail the addition of another glycosidic enzyme, such as a-L-arabinofuranosidase, to the genome of the wine yeast to aid the further breakdown of glycosidic bonds. The cloning or engineering of a j3-glucosidase enzyme that is more active at low temperatures would also yield better results and release even more of the aroma of the wine.
AFRIKAANSE OPSOMMING: Monoterpeenalkohole (monoterpenole) speel 'n belangrike rol in die geur en aroma van druiwe en wyn. Dit is veral van toepassing op wyne van Muskaat-varieteite, maar hierdie geurkomponente is ook teenwoordig in ander nie-Muskaat druifsoorte, waar dit bydra tot die varieteitsqeur en aroma. Hierdie monoterpenole kom voor in druiwe as vry, vlugtige en aromatiese molekules, of as geurlose, nie-vlugtige glikosidies-gebonde komplekse. Hierdie komplekse is meestal in die vorm van 6-0-a-L-arabinofuranosiel-~-D-glukopiranosiede, 6- O-~-D-xilopiranosiel-~-D-glukopiranosiede (primverosiede), 6-0-~-D-glukopiranosiel-~-Dglukopiranosiede (gentiobiosiede), 6-0-a-L-ramno-pyranosiel-~-D-glukopiranosiede (rutinosiede), of 6-0-~-D-apiofuranosiel-~-D-glukopirano-siede van hoofsaaklik linalool, geraniol, nerol, a-terpineol en hotrienol. Hierdie geurvoorlopers word egter slegs tot In beperkte mate tydens die proses van fermentasie deur die endogene glikosidase ensieme gehidroliseer, aangesien hulle baie min aktiwiteit toon onder wynbereidingstoestande. Die monoterpenole kan op een van twee wyses van hul suikermolekules vrygestel word: 'n suurhidrolise, of ensiematiese hidrolise. Die ensiematiese hidroliseproses word baie goed begryp en behels twee opeenvolgende stappe: eerstens, afhangende van die aard van die voorloper, word die glikosidiese verbinding deur In a-L-arabinofuranosidase, In a-L-ramnosidase, In ~-D-xilosidase, of 'n ~-D-apiosidase gebreek. In die tweede stap word die monoterpeenalkohol deur In ~-glukosidase vrygestel. Hierdie ensiematiese afbraakproses verander nie die intrinsieke aromatiese kenmerke van die wyn, soos wat met suurhidrolise die geval is nie. Omdat die endogene glikosidases van Vitis vinifera en die van die gis Saccharomyces cerevisiae baie lae aktiwiteit ten opsigte van die aromatiese voorlopers gedurende die hantering van die druiwesap en wynmaakprosesse toon, val die fokus al hoe meer op die inkorporering van eksogene ~-glukosidases in wyn en sappe. Gene wat vir ~- glukosidases en a-L-arabinofuranosidases kodeer, is al vanuit verskeie organismes gekloneer, insluitende bakteriee, fungi en giste. Die aktiwiteite en kenmerke van hierdie ensieme is egter nie altyd wenslik vir hul gebruik in wyn nie, aangesien dit In omgewing is met 'n lae pH, lae temperatuur, en hoe etanolvlakke en glukose-konsentrasies. In geneties veranderde wyngis van S. cerevisiae wat in staat is om glikosidases uit te druk wat onder hierdie kondisies aktief is, sal baie handig te pas kom in die verbetering van die geur en aroma van wyne, om daardeur die kompleksiteit en die waarde van die wyn te verhoog. Twee ~-glukosidasegene, BGL 1 en BGL2 vanaf die gis Saccharomycopsis fibuligera , is in twee afsonderlike Esccherichia coli-gis-pendelplasmiede gesubkloneer. In Dominante selekteerbare merkergeen (SMR1) is ook in hierdie plasmiede gekloneer. Hierdie plasmiede word onderskeidelik pBGL 1 (met die BGL 1-geen) en pBGL2 (bevattende die BGL2-geen) genoem. Hierdie twee plasmiede is hierna apart na twee rasse van S. cerevisiae getransformeer. Eerstens is 'n laboratoriumras, L1278, getransformeer om te bevestig dat effektiewe sekresie en uitdrukking van die proteTen plaasvind. Hierna is 'n industriele gisras, VIN13, getransformeer deur gebruik te maak van die selektiewe merker (bestandheid teen sulfometuron). Ensiem-bepalings met behulp van die sintetiese substraat p-nitrofeniel-p-O-glukopiranosied (pNPG) is gedoen om die aktiwiteit van die p-glukosidqses oor 'n aantal dae te bepaal, asook om die aktiwiteit by sekere temperature en pH-vlakke te meet. Die stabiliteit van die ensieme is ook bepaal. Hierdie rekombinante giste was in staat om pNPG effektief af te breek. Hulle het belowende resultate betreffende die pH-optima getoon, met 'n aansienlike hoeveelheid aktiwiteit by die pH-vlakke soos dit in die wynomgewing voorkom. Daar was ook 'n effense verhoging in die ensieme se aktiwiteite by laer temperature. Die rekombinante gisrasse is ook in kleinskaalse wynfermentasies gebruik. Drie verskillende wyne is gemaak, waarvan twee wit kultivars was (Chenin blanc en GewOrtztraminer) en een 'n rooi kultivar (Pinotage). Resultate wat deur die mikro-ekstraksie van die voltooide wyne verkry is, het getoon dat die terpenolinhoud wei verhoog het, alhoewel dit nie die enigste wynkomponente was wat beinvloed is nie. Ander geurkomponente het ook 'n verhoging in konsentrasie getoon, veral die esters. Hierdie verbindings het ook 'n rol in die verhoging van geur in die wyne gespeel. Toekomstige werk sal die beskikbare resultate verder optimaliseer. Dit sal insluit die byvoeging van nog 'n glikosidiese ensiem, soos a.-L-arabinofuranosidase, tot die genoom van die wyngis, om verdere afbraak van glikosidiese verbindings teweeg te bring. Die klonering of verandering van 'n p-glukosidase-ensiem met verhoogde aktiwiteit by laer temperature sal ook beter resultate toon en meer geur in die wyn kan vrystel.

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2009.
This study focused on a serious quality-related problem in the global wine industry, including the South African Wine Industry, namely cork taint in wine. Annually, large financial losses are incurred by cork suppliers and wine producers, as a result of cork-tainted wine. Although contaminated new unused corks are frequently implicated as the origin of this taint, contaminated cellar equipment and water can also be the source of the problem. An explorative investigation into the incidence of cork taint in South African wines showed that 3.8% of the 133 wines tested, contained 2,4,6-trichloroanisole (TCA) concentrations of 3.5 ng/L and higher, as determined by gas chromatography coupled with electron capture detection (GC-ECD). TCA concentrations higher than 1 ng/L were found in 18% of the wines tested. All affected wines were sealed with solid or agglomerate cork stoppers. These wines were sourced from various wineries in the Western Cape region, South Africa and were of different cultivars. None of the wines sealed with synthetic closures had any detectable TCA, 2,4,6-tribromoanisole (TBA) or pentachloroanisole (PCA) levels and only very low 2,3,4,6- tetrachloroanisole (TeCA) levels (1 ng/L or less). Another group of 28 wines that were rejected by the official South African wine regulatory body on the basis of the presence of mouldy taint during wine certification, was also included in this study. GC-ECD analysis showed that 30% of the wines in this group contained TCA at concentrations of 3.5 ng/L and higher. These results pointed to a relative high incidence of TCA in the wines investigated, especially those sealed with cork stoppers. Although no general conclusions should be made on the incidence of cork taint in the wider wine industry based on the results found within this explorative investigation, these findings confirmed the presence of cork taint in South African wines. Detection threshold values were determined for TCA, TeCA, TBA and PCA in three wine cultivars using the standard ASTM method. Results indicate that factors relating to the wine cultivar seemed to affect threshold values considerably. Our research proposes a detection range rather than an average detection threshold. Detection ranges established for TCA, TeCA, TBA and PCA in Chenin blanc, Pinotage and Shiraz coincide with reported values in literature. This result can be regarded as a valuable expansion of the existing knowledge of detection threshold values. Descriptive sensory analysis indicated significant (P 0.05) changes in the aroma profile of Chenin blanc, Pinotage and Shiraz after TCA, TeCA, TBA or PCA was added to the respective base wines that contained no detectable levels of the haloanisoles. The mouldy taint induced by these haloanisoles were described as mouldy, mouldy-chemical, mouldychlorine, as well as mouldy-acidic. In Chenin blanc, additions of TCA, in the concentration range 1 to 17 ng/L, resulted in a marked increase in the mouldy aroma and was accompanied by an immediate decrease in fruitiness. This change was already evident at added TCA concentrations of 1 ng/L. Similar trends were observed in Pinotage, while the addition of low levels of TCA to Shiraz (2 ng/L) resulted in a significant (P 0.05) decrease in the herbaceous character of the wine. The aroma changes observed were prominent enough to render the wine totally unacceptable in comparison to its original character. Consumers’ degree of liking did not seem to be affected by very low concentration levels of TCA in Chenin blanc, Pinotage or Shiraz, but rejection increased as the concentration increased beyond detection threshold level. A slight gender effect was also noticed. Female consumers appeared to be more sensitive to increasing levels of TCA, whereas male consumers did not respond as negatively to higher concentration levels of TCA. This study makes an important contribution towards understanding the sensory impact of especially TCA contamination in wine, through the establishment of concentration ranges at which these compounds exert a noticeable detrimental effect on the aroma profile of wine. Additional insight into cork taint in wine is provided by the consumer preference studies, where the effects of the taint on the product acceptance by consumers are demonstrated. The development of a modus operandi to ensure that sensory panels provide reliable data, can be regarded as an important contribution to wine-related research. This study is one of the first where advanced sensometric techniques were applied in sensory studies on cork tainted wines.

Thesis (Msc (Viticulture and Oenology. Institute for Wine Biotechnology))--University of Stellenbosch, 2009.
Monoterpenes are important aroma compounds in certain grape varieties such as Muscat, Gewürztraminer and Riesling and are present as either odourless, glycosidically bound complexes or as free aromatic monoterpenes. These complexes occur as monoglucosides or, when present as diglycosides, most commonly as 6-O-α-L-arabinofuranosyl-β-D-glucopyranosides of mainly linalool, geraniol, nerol and citronellol. The release of monoterpenes from non-volatile glycosidically bound precursors occurs either by acid hydrolysis or enzymatic hydrolysis. High temperature acid hydrolysis causes a rearrangement of the monoterpene aglycones and a decrease in the aroma and changes in the aromatic characteristics of monoterpenes and is therefore not suitable. Enzymatic hydrolysis does not modify the monoterpene aglycones and can be an efficent method to release potentially volatile monoterpenes. α-L-arabinofuranosidase and β-glucosidase are important enzymes responsible for the liberation of monoterpene alcohols from their glycosides. Glycosidases from Vitis vinifera and Saccharomyces cerevisiae are severely inhibited by winemaking conditions and this leads to unutilized aroma potential, while commercial preparations of aroma liberating enzymes are crude extracts that often have unwanted and unpredictable side effects. It is therefore of interest to investigate alternative measures to release glycosidically bound monoterpenes to increase the floral aroma of wine without side activities that impact negatively on wine. Heterologous α-L-arabinofuranosidases and β-glucosidases have previously been expressed in S. cerevisiae and these studies have evaluated and found increased glycosidic activities against both natural and synthetic substrates. In this study, we expressed the Aspergillus awamori α-L-arabinofuranosidase (AwAbfB) in combination with either the β-glucosidases Bgl2 from Saccharomycopsis fibuligera or the BglA from Aspergillus kawachii in the industrial yeast strain S. cerevisiae VIN13 to facilitate the sequential enzymatic hydrolysis of monoterpene diglycosides. Enzyme assays and GC-FID (Gas Chromatography with a Flame Ionization Detector) results show a significant increase in the amount of free monoterpene concentrations under winemaking conditions in the strain co-expressing the AwAbfB and the Bgl2. The increases in free monoterpene levels obtained were similar to those obtained with a commercial enzyme preparation, LAFAZYM AROM. Sensorial evaluation confirmed the improvement in the wine aroma profile, particularly the floral character. This yeast strain permits a single culture fermentation which improves the sensorial quality and complexity of wine. Further investigations on the factors influencing the stability and reactivity of monoterpenes during alcoholic fermentation are needed.

During 20th century main concern was to have sanitary water flowing through the tap. In 21st century constant supply of safe drinking water is common at any home in USA. Hence consumers pay attention to aesthetic quality of tap water. Odorous algal metabolites in source water and metals introduced to drinking water due to corrosion of pipes in the distribution system cause taste, odor and color problems, and result in complaints and perception of tap water as unhealthy. Millions of dollars are spent each year by water industry to address and prevent these issues. This research focused on some of the taste-and-odor issues associated with drinking water. First aim was to understand when geosmin, 2-MIB, and nonadienal become detectable, employing two-resistance mass transfer theory to determine the concentration of odorants in bathroom air. Results showed that water temperature and odorant concentration in water play an important role. Next focus was to develop an international odor standard to be used for training of sensory analysis panelists. There are many sensory methods to monitor drinking water to detect the off-flavors however an odor standard has been missing. Hexanal was studied with trained flavor profile analysis panels and was proposed as an ideal odor reference standard to be used for training and sensory assessment of water samples. Main focus was to understand metallic flavor of drinking water caused by iron and copper. It was shown that metallic sensation has taste and retronasal components creating the flavor and humans are very sensitive to it. Occurrence of lipid oxidation in the oral cavity was shown when metals were ingested, that produces carbonyls which are responsible for the metallic flavor. Antioxidants and chelators were investigated to study prevention of lipid oxidation and, chelators were determined to be more effective. Oral epithelial cell cultures were developed as a model for oral cavity to further investigate lipid oxidation and effectiveness of the antioxidants and chelators. This dissertation is a result of inter-disciplinary work and possibly a good example for how problems may be solved by incorporating different methods and point of views from several disciplines.
Ph. D.

Thesis (MScAgric)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: The distinctive varietal flavour of wines is a combination of absolute and relative concentrations of chemical compounds. Volatile compounds are responsible for the odour of wine and non-volatiles cause the sensation of flavour. Accompanying these senses, a third, tactile, sense of ‘mouth-feel’ is recognizable. This forms the complete organoleptic quality of wine. Several hundred different compounds are simultaneously responsible for the odour release in wine, and since there is no real character impact compound, the aroma of wine can be described as a delicate balance of all these compounds. One of the most important groups of volatiles is the monoterpenes, which play a role in both aroma and flavour. This is especially significant for the Muscat varieties, but these flavour compounds are also present in other non-muscat grape varieties, where they supplement the varietal aroma. Monoterpenes occur in wine as free, volatile and odorous molecules, as well as flavourless non-volatile glycosidic complexes. The latter slowly releases monoterpenes by acidic hydrolysis, but the impact on varietal aroma is considered insufficient for wines that are consumed young. It is therefore important to supplement the release mechanism, in order to enhance the varietal aroma of the wine. The enzymatic hydrolysis mechanism functions in two successive steps: firstly, depending on the precursor, the glycosidic linkage is cleaved by α-L-arabinofuranosidase, α-L-rhamnosidase, β-D-xylosidase or β-D-apiosidase. The second step involves the liberation of the monoterpene alcohol by a β-glucosidase. This enzymatic hydrolysis does not influence the intrinsic aromatic characteristics of the wine, as opposed to acid hydrolysis. Pectolytic enzymes play an important role in cell elongation, softening of tissue and decomposition of plant material. These enzymes are used to improve juice yields, release colour and flavour compounds from grape skins, as well as improve clarification and filterability. Pectolytic enzymes work synergistically to break down pectins in wine. Protopectinase produce water-soluble and highly polymerised pectin substances from protopectin, it acts on non-methylated galacturonic acid units. Pectin methylesterase split methyl ester groups from the polygalacturonic chain. Polygalacturonase break down the glycosidic links between galacturonic acid units. Pectin and pectate lyases have a β-eliminative attack on the chain and it results in the formation of a double bond between C4 and C5 in the terminal residues. From the above it can be seen that enzymes play a pivotal role in the winemaking process. Unfortunately, in winemaking a lot of factors can influence the effects of enzymes. One possible factor in the wine medium is the presence of acidprotease, from yeast and/or fungal origin. This type of enzyme utilizes other enzymes as substrates and renders them useless. Pure enzyme preparations were used to study the interactions of a yeast acid-protease and a report activity (β-glucosidase) in vitro. A bottled wine and a buffer were used as in vitro conditions. Enzyme assays were performed to determine the relative activity over a number of days. The results indicated that even though both enzymes showed activity in both the media, the yeast protease did not have any significantly affect on the report activity. Subsequently wine was made from Sauvignon blanc grapes, with varying enzyme preparation additions. Enzyme assays were performed during the fermentation; and chemical, as well as sensory analysis were done on the stabilized wine. The results confirmed that the yeast protease did not have any significant affect on the report activity in these conditions. The protease’s inability to affect the report activity seems unlikely due to the fact that it is active at a low pH range and has been suggested as the only protease to survive the fermentation process. It seems possible that a winerelated factor, possibly ethanol, is responsible. Thus it seems that yeast protease does not threaten the use of commercial enzymes in the winemaking process in any significant way. Future work would entail more detailed enzyme studies of interactions between protease, both from yeast and fungal origin, and other report activities in specified conditions. The degradation capability could be directed towards unwanted enzyme activities that cause oxidation and browning of the must. The characterization of interactions between protease and β-glucosidase activities may hold key to producing wines with enhanced aroma and colour potential, as well as the elimination of unwanted enzyme activities.
AFRIKAANSE OPSOMMING: Die herkenbare kultivar karakter van wyn is ‘n kombinasie van absolute en relatiewe konsentrasies van verskeie chemiese komponente. Vlugtige komponente is verantwoordelik vir die geur, of aroma, van wyn en die nie-vlugtige komponente veroorsaak die sensasie van smaak. ‘n Derde, fisiese sensasie, die ‘mondgevoel’, is ook herkenbaar. Dit vorm die omvattende organoleptiese kwaliteit van die wyn. ‘n Paar honderd verskillende komponente is gelyktydig verantwoordelik vir die aroma vrystelling in wyn en omdat daar geen werklike karakter ‘impak’ komponent is nie, kan die aroma van wyn beskryf word as ‘n delikate balans van al die betrokke komponente. Een van die mees belangrike groepe vlugtige komponente is die monoterpene wat ‘n rol speel in beide aroma en smaak. Dit is veral belangrik by Muskaat kultivars, maar hierdie aroma komponente is ook teenwoordig in niemuskaat druif kultivars, waar hulle bydra tot die kultivar karakter en aroma. Monoterpene kom in wyn voor as vry, vlugtige en aromatiese molekules en in geurlose, nie-vlugtige glikosidies-gebonde komplekse. Die gebonde vorm word stadig vrygestel deur ‘n suurhidrolise, maar dit word as onvoldoende beskou vir wyne wat vroeg gedrink word. Dit is dus belangrik dat die vrystelling van geurstowwe verhoog word om die kultivar karakter van die wyn te versterk. Die ensiematiese hidrolise proses behels twee opeenvolgende stappe: eerstens, afhangende van die aard van die voorloper, word die glikosidiese verbinding deur α-L-arabinofuranosidase, α-Lramnosidase, β-D-xilosidase, of β-D-apiosidase gebreek. In die tweede stap word die monoterpeen-alkohol deur β-glukosidase vrygestel. Hierdie ensiematiese afbraak proses verander nie die intrinsieke aromatiese kenmerke van die wyn, soos met suurhidrolise die geval is nie. Pektolitiese ensieme speel ‘n fundamentele rol in selverlenging, sagwording en afbraak van plant materiaal. Hierdie ensieme word gebruik om sap opbrengs te verhoog, aroma en smaak komponente vry te stel uit die doppe, asook om sapverheldering en filtrasie te verbeter. Die pektolitiese ensieme werk op ‘n sinergistiese wyse om pektien in wyn af te breek. Protopektinase produseer wateroplosbare en hoogs gepolimeriseerde pektien uit protopektien, slegs uit niegemetileerde galakturoonsuur eenhede. Pektien metielesterase verwyder metielester groepe van die poligalakturoonsuurketting. Die glikosidiese bindings tussen galakturoonsuur eenhede word deur poligalakturonase afgebreek. Pektien- en pektaat-liase het ‘n β-eliminasie aanslag op die ketting en as gevolg daarvan word dubbelbindings tussen C4 en C5 in die terminale residue gevorm. Vanuit bogenoemde is dit dus duidelik dat ensieme ‘n kardinale rol speel in die wynbereidingsproses. Ongelukkig is daar ‘n verskeidenhied van faktore wat die werking van ensieme in die wynbereidingsproses kan beïnvloed. Een moontlike faktor is die teenwoordigheid van ‘n suur-protease, van fungisidiese en/of gis oorsprong, in die wynmedium, omdat dit ander ensieme as substraat kan benut en degradeer. Suiwer ensiem preparate is gebruik om die ensiem interaksie tussen ‘n gis suur-protease en ‘n verslag aktiwiteit (β-glukosidase) in vitro te ondersoek. ‘n Gebotteleerde wyn en ‘n buffer is gebruik om die in vitro kondisies na te boots. Relatiewe ensiem aktiwiteit is ontleed oor ‘n aantal dae. Beide die ensieme het aktiwiteit getoon in die media, maar gis protease het geen statisties beduidende invloed gehad op die aktiwiteit van die verslag ensiem nie. Daaropvolgend is wyn berei van Sauvignon blanc druiwe, met verskillende ensiempreparaat toevoegings. Die ensiemaktiwiteit is deurlopend tydens fermentasie gemeet. Na afloop van stabilisasie is chemiese, sowel as sensoriese ontledings op die wyn gedoen. Die resultate het bevestig dat gis protease, onder hierdie kondisies, geen beduidende invloed op die verslag aktiwiteit gehad het nie. Die protease se onvermoë om die verslag aktiwiteit beduidend te beinvloed blyk onwaarskynlik aangesien die suurprotease aktief is by lae pH vlakke en dit as die enigste protease voorgestel is wat die fermentasie proses kan oorleef. Dit blyk asof ‘n wyn-verwante faktor, moontlik etanol, hiervoor verantwoordelik kan wees. Dus hou protease geen gevaar in vir die gebruik van kommersiële ensieme in wynbereiding nie. Navorsing kan in die toekoms fokus op meer gedetailleerde ensiem interaksie studies tussen protease en ander ensiem aktiwiteite, in gespesifiseerde kondisies. Die degradasie kapasiteit kan moontlik aangewend word om ongewenste ensiem aktiwiteite, wat byvoorbeeld oksidasie en verbruining veroorsaak, te verminder. Die karakterisering van die interaksies tussen protease en β-glukosidase kan dus die sleutel wees tot die produksie van wyne met verhoogde aroma potensiaal, asook die eliminasie van ongewenste ensiematiese aktiwiteite.

Thesis (MSc (Wine Biotechnology))--University of Stellenbosch, 2009.
The PGU1 gene encodes an endo-polygalacturonase, an enzyme that degrades pectin. Although the presence and function of this gene is well characterized in Saccharomyces cerevisiae, its regulation is very complex and not yet fully understood. Yeast producing a highly active polygalacturonase (PG) during alcoholic fermentation could potentially improve filtration and turbidity and also enhance extraction of certain aroma compounds. This could replace the addition of expensive commercial enzyme preparations that often contain unwanted enzymes. The first objective of this study was to evaluate PGU1 expression in recombinant strains of S. cerevisiae that originally lacked the PGU1 gene. A functional PGU1 gene and its promoter were successfully re-introduced into their native position in the genomes of five wine strains. Three of these strains recovered PG activity while two did not transcribe the gene and subsequently lacked activity. The three strains that recovered activity were used in microvinification experiments to determine the effect of PG-producing yeast on the aroma profile of the wine. No significant differences were observed in the volatile compounds production between the recombinants and their respective wild types, but some tendencies arose, especially for the monoterpene geraniol. The second objective of this study was to analyze the PGU1 gene and promoter from Saccharomyces paradoxus RO88 (a strain that exhibits high PG activity) and to compare it to those of S. cerevisiae S288C in order to identify differences that could potentially be responsible for the difference in their PG activities. Comparison of the gene sequences revealed several amino acid differences, one of which was in the peptide secretion signal. Analyses of the promoters also indicated some potentially important differences. Furthermore, S. cerevisiae strain VIN13, RO88 as well as two interspecies hybrids (all displaying varying PG activities) were compared under winemaking conditions. Clear differences were observed for the production of certain compounds. RO88 and the hybrids produced higher concentrations of certain volatile compounds, although they were not strong fermenters. Two recombinants, each containing a PGU1-overexpressing plasmid (one with the PGU1 gene from S. paradoxus and the other from S. cerevisiae), were also used in vinification to determine the effects of the different PGU1 gene on the aroma profile of the wine. Unfortunately, the plasmids were unstable and lost during the fermentation. Nevertheless, some tendencies were observed that indicated possible higher production of certain compounds by the recombinants compared to their wild types. This study identified that regulation of the PGU1 gene differs between strains with different genetic backgrounds. Certain differences were observed in the PGU1 gene and promoter sequences between S. cerevisiae and S. paradoxus that could potentially be the reason for the difference in their PG activities. From an oenological point of view, the presence of PGU1 in the genome of a fermenting strain tends to increase the aromatic potential of wine. These results provide a good platform for further studies on the PGU1 gene.

O mercado cervejeiro passa por uma revolução voltada à produção em escala artesanal ao invés de escala industrial, devido às expectativas dos consumidores em busca de alta qualidade e novo sabor do produto final. Visando produzir uma cerveja leve com relação ao teor de extrato e álcool, com sabor diferenciado, foram realizados vários ensaios de adição de gengibre no processo de produção. O mais viável resultado foi obtido com adição de 2g L-1 de lascas de gengibre in natura na maturação. A cerveja artesanal adicionada de gengibre foi produzida em escala laboratorial, para permitir sua análise físico-química e análise sensorial. Paralelamente, foram analisadas outras vinte e oito amostras de cerveja Pilsen para efeitos comparativos com relação aos aspectos físico-químicos. De acordo com o resultado do teste sensorial, o índice de aceitabilidade global foi de 92%, estando também acima de 70% o índice dos atributos individuais avaliados. A cerveja artesanal adicionada de gengibre apresentou características mais próximas às amostras de “Cerveja” ao invés das amostras “Puro Malte”, segundo classificação com relação ao teor de malte, por meio de análises quimiométricas (PCA e HCA). Essa discriminação entre os grupos foi devida aos teores de álcool, grau real de fermentação, grau aparente de fermentação, potássio, calorias e magnésio. O produto final apresentou como características principais um baixo teor alcoólico (3,40o GL), baixo valor energético (115,44 KJ 100 mL-1) e extrato reduzido (7,81º Plato). Apesar do amargor mais acentuado (21,55 B. U.), o índice de aceitabilidade para o amargor permaneceu acima de 70%, com flavor picante e aromático.
The brewing market undergoes a revolution directing to production on a homemade scale rather than an industrial scale, due to the expectations of consumers searching high quality and new flavor of the final product. In order to produce a light beer with respect to the extract and alcohol content and different flavor, several ginger addition tests were carried out in the production process. The most viable result was obtained with addition of 2 g L-1 of ginger flakes in natura at maturation. The artisanal brewed beer of ginger was produced in laboratory scale, to allow its physical-chemical analysis and sensorial analysis. In parallel, others twenty-eight samples of Pilsen beer were analyzed for comparative purposes in relation to physico-chemical aspects. According to the result of the sensorial test, the overall acceptability index was 92% as also as individual attributes evaluated were also above 70%. The artisanal beer added with ginger showed characteristics closer to the "Beer" samples than the "Pure malt" samples, according to classification in relation to the malt content, by means of chemometric analyzes (PCA and HCA). This discrimination between groups was due to alcohol, real degree of fermentation (RDF), apparent degree of fermentation (ADF), potassium, calories and magnesium. The final product had a low alcohol content (3.40 oGL), low energy (115.44 KJ 100 mL-1) and reduced extract (7.81 oPlato). Despite the more pronounced bitterness (21.55 B. U.), the acceptability index forbitterness remained above 70%, with spicy and aromatic flavor.

O sabor da cerveja é determinado pela matéria-prima, pelo tipo de processo e pela levedura utilizada, além dos compostos produzidos durante a fermentação e maturação, que exercem maior impacto. A produção de amidos modificados é uma alternativa praticada com o objetivo de superar limitações dos amidos nativos e aumentar a utilidade deste polímero em aplicações industriais. O objetivo da pesquisa foi avaliar a aplicação de amidos de milho e mandioca modificados (fosfatação e oxidação) no processo de clarificação de cerveja artesanal, visando a obtenção de uma cerveja “limpa” e translúcida. Foram elaboradas oito cervejas testando os amidos aniônicos: amido de milho oxidado 1% (MiO 1%); amido de milho oxidado 2% (MiO 2%); amido de mandioca oxidado 1% (MaO 1%); amido de mandioca oxidado 2% (MaO 2%); amido de milho fosfatado baixo (MiFB); amido de milho fosfatado alto (MiFA); amido de mandioca fosfatado baixo (MaFB); amido de mandioca fosfatado alto (MaFA). Essas amostras foram comparadas com uma cerveja submetida ao mesmo processo utilizando o clarificante goma carragena (GCar) e com uma cerveja sem adição de clarificante (SC). As amostras foram submetidas às análises de compostos fenólicos, flavonóides, biureto, espectrofotometria, turbidez e viscosidade relativa para verificar a possível ação clarificante. Foi realizada a caracterização físico-química das amostras de cerveja artesanal (pH, extrato real, acidez, teor alcóolico, extrato primitivo e grau real de fermentação). A aplicação de amidos modificados reduziu o teor de compostos fenólicos, flavonóides, proteínas, e a viscosidade relativa no decorrer do processo. Além disso, a clarificação foi notada nas análises de turbidez e espectrofotometria. Pode-se concluir que alguns amidos destacaram-se, superando os resultados apresentados pela goma carragena na etapa final do processo. No entanto, notou-se que a eficiência destes amidos ocorre a partir da maturação, diferente da goma carragena que clarifica principalmente na etapa da fervura. Em um aspecto global, sugere-se que na fosfatação, a fonte botânica não influenciou, e as amostras destaques na clarificação foram o amido de milho fosfatado baixo (2,8%) (amostra 7), o amido e milho fosfatado alto (8,6%) (amostra 8) e o amido de mandioca fosfatado alto (amostra 10). Para a oxidação a amostra que apresentou melhor desempenho foi o amido de mandioca oxidado 1% (amostra 4).
The flavor of beer is determined by the feedstock, the type of process and the yeast used, in addition to the compounds produced during fermentation and maturation, that ecxercises greater impact. The production of modified starch is an alternative practiced with the aim of overcoming the limitations of the native starches and increase the usefulness of this polymer in industrial applications. The objective of the research was evaluate the application of corn and cassava modified starches (phosphatation and oxidation) in the craft beer clarification process to getting a beer "clean" and translucent. Were elaborated eight beers testing the anionic starches: oxidized corn starch 1% (MiO 1%); oxidized corn starch 2% (myo 2%); oxidized cassava starch 1% (MaO 1%); oxidized cassava starch 2% (MaO 2%); phosphate corn starch low (MiFB); phosphated corn starch high (MIFA); phosphated cassava starch low (MAFB); phosphate cassava starch high (MAFA). These samples were compared with a beer submitted to the same process using the clarifier carrageenan gum (CARG) and with a beer without added clarifier (SC). The samples were submitted to analysis of phenolic compounds, flavonoids, biuret, spectrophotometry, relative viscosity and turbidity to verify possible clarifier action. Was realized physicochemical characterization of craft beer samples (pH, real extract, acidity, alcohol content, original extract and real degree of fermentation). The application of modified starches reduced the content of phenolic compounds, flavonoids, proteins, and the relative viscosity during the process. In addition, the clarification was noted in turbidity analysis and spectrophotometry. It can be concluded that some starches stood out, overcoming the results presented by carrageenan gum in the final stage of the process. However, it was noted that the efficiency of these starches occurs from the maturation, different of carrageenan gumthat clarifies mainly in the boiling step. In a global aspect, it is suggested that in the phosphatation, the botanical source did not influence, and the highlight samples in clarification were phosphated corn starch low (2.8%) (sample 7), phosphated corn starch high (8 , 6%) (sample 8) phosphated cassava starch high (sample 10). To the Oxidation. the sample that showed better performance was oxidized cassava starch 1% (sample 4).

A preliminary trial to determine the effect of repeated freezing and thawing on beef striploins, showed that the effect of thawing on frozen non-aged beef significantly improved tenderness, flavour and acceptability, indicating that thawing had a similar effect to aging. In the subsequent study, 207 beef striploins were collected from the Southern Crossbreeding Project (SXB: 70 heifers grainfed for 80 days, 70 steers grainfed for 180 days), Davies Gene Mapping Project (DGM: 30 steers grainfed for 180 days) and also 37 Hanwoo striploins imported into Australia from Korea. SXB animals consisted of Hereford cross calves sired by Belgian Blue, Limousin, South Devon, Hereford, Angus, Wagyu and Jersey bulls. DGM animals consisted of purebred Limousins and Jerseys and Limousin by Jersey crosses. Sensory analysis of beef striploins involved semi-trained taste panel assessments, using nine-point category scales for initial and sustained juiciness, beef flavour, beef fat flavour, oily flavour, buttery flavour, chicken-skin flavour, corn flavour, grassy flavour and overall acceptability. Flavour acceptability was positively enhanced by increased levels of intramuscular fat (IMF%). Significant differences in breed were apparent for juiciness, beef flavour, buttery flavour and flavour acceptability, after adjusting data to a constant level of intramuscular fat, suggesting that some variation in flavour may be genetic. The Korean Hanwoo displayed a numerically higher intensity of chicken score and lower intensity of beef flavour. Australian cattle breeds differed in fatty acid composition between each other and also to that of the Korean Hanwoo. The latter had 57% mono-unsaturated fatty acids, which was significantly higher (P<0.001) than the Australian breeds (47%). Since IMF% was confounded with breed, breed differences were not significant when adjusted for IMF%. Jersey animals most closely resembled the Hanwoo in fatty acid profile, whilst animals containing Limousin differed markedly from the Hanwoo. A chemical sensor was able to establish significant differences between Korean Hanwoo and Australian animals and predominantly mirrored differences in fatty acid composition and to some extent flavour. Development of prediction equations from individual fatty acids was disappointing (R2< 15%). However, when fatty acid data, IMF% and chemical sensor data were combined to form prediction equations, moderate R2 values were obtained of (24% to 43%).
Thesis (M.Ag.Sc.)--School of Agriculture & Wine, 2001.

Odor detection thresholds of hexanal, 2-heptenal, 2-pentanone, and 2,4-nonadienal were determined in spring water, high temperature short time (HTST) 2% fat milk, and extended shelf life soymilk. The efficacy of odor scavenger's beta-cyclodextrin, D-sorbitol, and nylon 6 in removing these odors was also determined. The odor thresholds of the different odor and media combinations were as follows: hexanal in spring water, milk, and soymilk were 585, 339, and 536 ppb respectively; 2-heptenal in spring water, milk, and soymilk were 2,092, 2,322, and 3,184 ppb respectively; 2-pentanone in spring water, milk and soymilk were 24,925, 29,255 and 33,271 ppb respectively; and 2,4-nonadienal in spring water, milk, and soymilk were 164, 326, and 243 ppb respectively. These amounts reference the initial spiked concentration that was added directly to the media. Both hexanal and 2,4-nonadienal had lower thresholds than 2-heptenal and 2-pentanone in all of the media. The odor detection thresholds of 2-heptenal, 2-pentanone, and 2,4-nonadienal did show a significant difference between soymilk and water, but not for milk. The efficacy of the odor scavengers were determined by use of solid phase micro-extraction gas chromatography (SPME-GC) and sensory evaluation. Hexanal, 2-heptenal, 2-pentanone, and 2,4-nonadienal were spiked at 1,000, 3,000, 30,000, and 300 ppb respectively in all three media. Beta-cyclodextrin, D-sorbitol, and nylon 6 were added at a level of 0.1% w/v and 1.0% w/v. In all of the media, beta-cyclodextrin was found to significantly reduce hexanal, 2-pentanone, 2-heptenal, and 2,4-nonadienal at both 0.1% w/v and 1.0% w/v. Nylon 6 was not found beneficial.
Master of Science

For water suppliers, using chlorine is necessary to ensure water bacteriological quality from the treatment plant to the consumers' tap. However, chlorine flavour is one of the most common reasons advocated for choosing tap water alternatives as drinking water. As a consequence, the putative link between chlorine flavour perception and tap water consumption is an issue in drinking water habits studies. Since the sensory mechanisms involved in chlorine flavour perception remained largely unknown, the main objective of this thesis work was to first highlight those mechanisms and then to identify potential lever chlorine flavour sensory neutralisation.In a first step, we demonstrated that hypochlorous acid associated, which is likelyresponsible of chlorine flavour in tap water, could activate the olfactory system at low concentrations and the trigeminal system for concentrations up to 4 mg/L Cl2. Additionally, our results suggested that tap water consumption does not seem to be related to sensitivity to chlorine flavour but rather to consumers' tap water representation.In a second stage, we explored the impact of water mineral matrix on chlorine flavour perception. We demonstrated first that water molarity and cationic content variations modulate drinking water taste. We also evidenced that chlorine flavour intensity is modulated according to water composition. Nevertheless, our data suggest that physico-chemical, in- mouth physiological and sensory mechanisms are likely involved in such modulation.In the last part of the Thesis work, we investigate the putative influence of aroma perceptionon chlorine flavour. Our results showed that beyond chemical reactions between hypochlorous acid and odorants, aromas at peri-threshold concentration enhance chlorine flavour and decrease tap water acceptability

Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Scotch whiskey is of two main types, namely Scotch malt whiskey, made from malted barley alone, or Scotch grain whiskey, made from cereals, such as wheat or maize, together with malted barley. In both processes, the enzymes from the barley are responsible for starch conversion and should always be derived entirely from the malted barley. No exogenous enzymes are allowed to be added to any mashing. The enzymes involved in the conversion process to fermentable sugars, are the aand p-amylases, limit dextrinase and p-glucosidase. Maize, on the other hand, contains no enzyme activity, therefore enzymes need to be added when producing whiskey from maize alone. In other whiskey-producing countries where maize is freely available and cheaper than barley, the use of exogenous enzymes are allowed in the mashing process and is crucial for the formation of fermentable sugars from complex carbohydrates. The cost of the enzymes, however, can push the production cost of whiskey to higher levels. Saccharomyces cerevisiae does not have any amylolytic activity, but is an excellent fermenter and produces favourable organoleptic notes, which makes it very suitable for producing potable spirit. Efforts have been made to genetically improve industrial strains, relying on classical genetic techniques followed by the selection of broad traits, such as ethanol tolerance, absence of off-flavours and carbohydrate/starch utilisation. No strain has thus far been selected for total starch degradation during the fermentation of whiskey mash. Over the last decade, considerable progress has been made in the development of genetically improved strains for the distilling, wine, brewing and baking industries. The expression of heterologous genes introduced a new dimension in approaches to the genetic improvement of industrial strains. It would therefore be cost-effective to use a yeast strain that can produce active and sufficient enzymes to ferment raw starch efficiently to alcohol without lowering the quality of the end product. No such strain has been developed to date, but the continuous improvement of starch-utilising strains has made this goal more achievable. Two a-amylase genes, namely LKA 1 and LKA2, were previously isolated from Lipomyces kanonenkoae. In this study, we selected 4 strains on the basis of criteria that are important for whiskey-specific strains. The selected strains were transformed with LKA 1, as well as with a combination of LKA 1 and LKA2 genes. The wine yeast VIN13 was included in the transformation of LKA1 and LKA2 because of its rapid fermentation rate. The genes were integrated into the genomes of the yeast strains and were stable after many generations. Assays showed that a significant increase in enzyme activity was induced in the whiskey strains, compared to the untransformed strains. The strains also showed good fermentation ability in whiskey fermentations, although optimum alcohol production was still not achieved.
AFRIKAANSE OPSOMMING: Skotse whiskey bestaan uit 2 tipes, nl. mout whiskey, gemaak slegs van mout d.w.s. gars wat die mout proses ondergaan het, en graan whiskey wat gemaak word van gewasse soos mielies of koring, waarby mout gevoeg word. Die ensieme afkomstig van die mout is verantwoordelik vir die omsetting van stysel na fermenteerbare suikers en geen eksogene ensieme mag by die gars- of graanmengsel gevoeg word nie. Die ensieme wat betrokke is by die omsetting van stysel, is die a- en ~- arnitases, limiet dekstrinase en ~-glukosidase. Mielies bevat geen ensiemaktiwiteit nie, dus moet ensieme by die proses gevoeg word indien slegs mielies vir die vervaardiging van whiskey gebruik word. In whiskey produserende lande waar mielies vryelik beskikbaar is en goedkoper is as gars, word eksogene ensieme by die graanmengsel gevoeg vir die vrystelling van fermenteerbare suikers vanaf komplekse koolhidrate. Die hoë koste van die ensieme kan egter die produksiekoste van whiskey verhoog. Saccharomyces cerevisiae besit geen amilolitiese aktiwiteit nie, maar is 'n uitstekende fermenteerder en produseer gewensde organoleptiese geure. Om hierdie redes is S. cerevisiae baie geskik vir die produksie van drinkbare etanol. Navorsingspogings om industriële rasse geneties m.b.v. klassieke genetiese metodes te verbeter, kom wydverspreid in die literatuur voor. Dit sluit in die seleksie van rasse met 'n verskeidenheid van eienskappe soos etanol toleransie, die afwesigheid van afgeur produksie en koolhidraat/stysel benutting. Geen ras is egter tot op hede geselekteer vir totale stysel afbraak gedurende fermentasie nie. Groot vordering is gedurende die laaste dekade gemaak in die ontwikkeling van genetiese verbeterde rasse vir die wyn- stokery- en brouers industrieë. Die uitdruk van heterogene gene in gisrasse gee 'n nuwe dimensie aan die genetiese verbetering van industriële rasse. Die gebruik van 'n gisras wat aktiewe en genoegsame ensieme produseer om rou stysel te fermenteer, sonder om die kwalitiet van die eindproduk nadelig te beïnvloed, kan die produksiekoste van whiskey aansienlik verminder. Geen gisras met hierdie eienskap is tot op hede ontwikkel nie, maar die voortdurende verbetering van rasse om stysel af te breek maak hierdie doel meer bereikbaar. Twee a-amilase gene, nl. LKA 1 en LKA2 is voorheen uit Lipomyces kononenkoae geïsoleer. In hierdie studie is 4 gisrasse geselekteer op grond van die kriteria wat nodig is vir whiskey giste. Die geselekteerde rasse is getransformeer met LKA 1 sowel as 'n kombinasie van LKA 1 en LKA2 gene. Die wyngis VIN13 is ingesluit by die transformasie met die LKA1 en LKA2 gene, omrede VIN13 bekend is as 'n vinnige fermenteerder. Die gene is geïntegreer in die genoom van die verskillende gisrasse en is stabiel na vele generasies. Die getransformeerde rasse het 'n betekenisvolle verhoging in ensiemaktiwiteit teenoor die nie-getransformeerde rasse getoon. AI die transformante het ook goeie fermentasie vermoë getoon in whiskey fermentasie proewe. Optimum alkoholproduksie is egter nie verkry nie.

In recent years, communities that source raw water from the Dan River experienced two severe and unprecedented outbreaks of unpleasant tastes and odors in their drinking water. During both TandO events strong 'earthy', 'musty' odors were reported, but the source was not identified. The first TandO event began in early February, 2015 and coincided with an algal bloom in the Dan River. The algal bloom was thought to be the cause, but after the bloom dissipated, odors persisted until May 2015. The second TandO in October, 2015 did not coincide with observed algal blooms. On February 2, 2014 approximately 39,000 tons of coal ash from a Duke Energy coal ash pond was spilled into the Dan River near Eden, NC. As there were no documented TandO events before the spill, there is concern the coal ash adversely impacted water quality and biological communities in the Dan River leading to the TandO events. In addition to the coal ash spill, years of industrial and agricultural activity in the Dan River area may have contributed to the TandO events. The purpose of this research was to elucidate causes of the two TandO events and provide guidance to prevent future problems. Monthly water samples were collected from August, 2016 to September, 2017 from twelve sites along the Dan and Smith Rivers. Multivariate analyses were applied to look for underlying factors, spatial or temporal trends in the data. There were no reported TandO events during the project but sensory analysis, Flavor Profile Analysis, characterized earthy/musty odors present. No temporal or spatial trends of odors were observed. Seven earthy/musty odorants commonly associated with TandO events were detected. Odor intensity was mainly driven by geosmin, but no relationship between strong odors and odorants was observed.
Master of Science

Thesis (PhD)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Key research areas in modern enology are related to the production of wine of consistent quality, as well as to the improvement of existing wine quality through the enhancement of the sensory properties of wine. The formation of glycerol during alcoholic fermentation is highly relevant to both these issues. Since the early years of the zo" century, glycerol has been positively associated with the quality of wine and it is thought to impart important mouth-feel sensations such as "viscosity", "smoothness" and "body". In general, it is considered that glycerol concentrations higher than those normally found in wine, can contribute towards the improvement of wine quality. It has also been suggested that increased concentrations of glycerol can enhance the aroma of wine. On the basis of these perceptions, several strategies have been developed to favour the production of glycerol during the fermentation process and over a period of years, a large volume of data has been collected that relates to various aspects regarding glycerol production during alcoholic fermentation. To date, however, several aspects regarding the relationship between glycerol and wine quality remain unclear. The reasons for this situation can mainly be ascribed to the lack of reliable analytical data to serve as a basis for investigating the relationship between glycerol and wine quality, as well as the preponderance of empirical and anecdotal evidence. Despite numerous opinions regarding optimal glycerol concentrations in wine, glycerol is indeed seldom assayed on a routine basis and targets with respect to specific wine grape cultivars and glycerol concentrations have largely remained unspecified. To date, very little information regarding glycerol concentrations in South African wines has been published. The analytical techniques that are most frequently used for the quantification of glycerol in grape juice, fermenting must and wine are not easily automated and this aspect placed severe limitations on the generation of large volumes of analytical data on glycerol concentrations in these matrices. This project was undertaken with the aim to holistically address some of the unresolved issues relating to the relationship between glycerol and wine quality. This also implied the development and optimisation of analytical techniques suitable for the rapid and accurate determination of glycerol in fermentation media, as well as in finished wine. In the first stage of this project a quantitative database was established that contained the analytical data on the glycerol concentrations of a statistically significant number of wines of adjudged quality, as well as additional information for each wine regarding the geographic origin, vintage, routine chemical analyses and the yeast strain(s) used for the production of the wine. The relevance of glycerol in wine for the modern South African winemaker was evaluated through the establishment of a quantitative database that contained the opinions of an expert panel of 15 South African winemakers, enologists and wine chemists on topics relating to glycerol in wine. In the second stage of the project the data captured in the databases were used to investigate aspects regarding the relationship between glycerol and wine quality. From the data captured in the qualitative database, it was clear that the topic regarding glycerol in wine was important to the South African winemakers and it was also evident that there was a need for the development and optimisation of methods suitable for the routine analysis of the glycerol concentrations in grape juice, fermenting must and wine. The opinions of the panel members also highlighted the issue that the mouth-feel property of wine was considered to be an area where the quality of some wines could be further improved. The quantitative database contained the information on the glycerol concentrations of 450 commercial South African table wines of adjudged quality. The premium cultivars Chardonnay, Chenin blanc, Sauvignon blanc, Cabernet Sauvignon, Merlot, Shiraz and Pinotage were used for the purpose of investigating the relationship between glycerol concentration and wine quality. The wines represented a wide variety of wine styles, including dry white, off-dry white, dry red and late harvest wines. The average glycerol concentration was significantly associated with the wine style. In white wines the average glycerol concentration was much lower than in the red wines (6.82 gIL versus 10.49 gIL, respectively). No significant relationship between the final glycerol concentration and the geographic origin, vintage and the yeast strain used for the fermentation was found. Wine quality could not be significantly associated with glycerol concentration in the red wines. In the white wines, the relationship between glycerol concentration and wine quality was significant, but due to the very small differences in the average glycerol concentrations of the wines of different quality ratings, the statistical significance is probably of little practical value. The effect of glycerol on the volatility of a selection of esters and higher alcohols was also investigated. Solid-phase microextraction, followed by gas chromatography, was used to analyse the composition of the headspace at equilibrium between the liquid phase and the gas phase of a model wine, and a dry white wine that contained a basal concentration of 5.4 gIL glycerol. Results showed that incremental increases in the glycerol concentrations over a range of 1 -10 gIL in the model wine and in a Chenin blanc wine, were not accompanied by a proportional increase or decrease in the abundance of the aroma components in the headspace. The volatile components tested were isoamyl acetate, ethyl butyrate, ethyl valerate, ethyl lactate, ethyl hexanoate, hexyl acetate, isoamyl alcohol and isobutanol. For all the volatile components tested, the difference between the headspace composition of samples containing the lowest glycerol concentration, and those containing the highest glycerol concentration, was not significant. However, sufficient experimental evidence was obtained to indicate that increasing glycerol concentrations had an effect on the volatility of aroma components, and that the effect is of a complex and non-linear nature. In the third phase of the work Fourier transform infrared spectroscopy (FT-IR) was used to establish and optimise methods for the accurate and rapid quantification of glycerol in wine. For this purpose calibrations were developed for the quantification of glycerol in dry wine and late harvest wines. The accuracy of prediction was evaluated by means of the standard error of prediction that was 0.38 gIL for the dry wines and 0.65 gIL for the sweet wines. Large variations are introduced in the FT-IR spectra of wine by factors such as process technology, cultivar and geographic origin, and this variation can have an effect on the accuracy of the analytical data generated when employing FT-IR spectroscopy. Using glycerol prediction in wine as a model system, principal component analysis of the FT-IR spectra was done in order to establish quality control measures for the detection of poorly predicted, or outlier samples. A classification model, based on principal component analysis, was established that enabled the interpretation and classification of the outlier samples in the data set in 100% of the cases tested. This work forms the basis for expanding the quality control measures for the detection of wines of which the FT-IR spectra are highly unnatural, as well as for establishing quality control measures to ensure that accurate analytical data are generated when FT-IR is used. FT-IR spectroscopy was also used to develop a rapid screen for the evaluation of the fermentation profiles of wine yeasts. For this purpose, a selection of wine yeasts, which included commercial wine yeasts frequently used in winemaking in South Africa, as well as a selection of hybrid Saccharomyces cerevisiae yeasts, that were obtained through a selective breeding strategy aimed at increasing glycerol concentrations were used. Calibrations necessary for the accurate quantification of glycerol, volatile acidity, ethanol, reducing sugar and glucose, in Chenin blanc must and a synthetic must were developed and optimised. This work forms the basis upon which the scope of the analysis, both in terms of the number of components that can be measured, as well as the medium in which the yeasts are being evaluated, can be enlarged. This would be valuable for future applications in both the research as well as the industrial environment. The method that was developed serves to illustrate how this application can play a supportive role in yeast development programmes, through the speeding up of the initial stages of yeast strain evaluation.
AFRIKAANSE OPSOMMING: Navorsing in moderne wynkunde is sterk gefokus op die produksie van wyn waarvan die kwaliteit van In volhoubare goeie peil is, sowel as die verdere verbetering van bestaande wynkwaliteit, deur In verhoging van die sensoriese eienskappe van wyn. Die vorming van gliserol tydens alkoholiese fermentasie het betrekking op beide hierdie aspekte. In Opvatting wat wyd gehuldig word en wat reeds sedert die vroeë jare van die 20e eeu geld, impliseer dat gliserol In positiewe bydrae lewer tot wynkwaliteit. Oor die algemeen word dit beskou dat gliserolvlakke hoër as wat normaalweg in wyn aangetref word, kan bydra om die kwaliteit van die wyn nog verder te vehoog. Daar is ook spekulasie dat verhoogde gliserolvlakke in wyn die intensiteit van die aroma van wyn kan verhoog. Hierdie opvattings het tot gevolg gehad dat veskeie strategieë ontwikkel is om die gliserol vlakke wat tydens die fermentasieproses gevorm word, te verhoog. Baie min inligting oor die gliserolinhoud van Suid-Afrikaanse wyn is tot onlangs gepubliseer. Ten spyte van die opvattings oor gliserol en wynkwaliteit wat reeds oor In lang tydperk gehuldig word, bly sekere aspekte van die verwantskap tussen gliserol en wynkwaliteit nog steeds onduidelik. Redes vir hierdie situasie kan hoofsaaklik toegeskryf word aan die totale afwesigheid van betroubare en substansiële eksperimentele data wat as basis kan dien vir die evaluering van die algemene opvattings aangaande die verwantskap tussen gliserol en wynkwaliteit. Die inligting wat wel beskikbaar is, is verder ook oorwegend van In empiriese aard. Huidig word gliserol selde op In roetine basis in die analitiese laboratorium bepaal, hoofsaaklik omdat die bestaande metodes tydrowend is en nie maklik geoutomatiseer kan word nie. In hierdie studie is In kwantitatiewe databasis opgestel waarin die inligting ten opsigte van die gliserolvlakke van 450 kommersiële Suid-Afrikaanse tafelwyne waarvan die kwaliteit beoordeel is, vervat is. Die kultivars Chardonnay, Chenin blanc, Sauvignon blanc, Cabernet Sauvignon, Merlot, Shiraz en Pinotage is gebruik vir hierdie doel en die seleksie van wyne was verteenwoordigend van In wye verskeidenheid wynstyle, insluitende droë wit-, halfdroë wit-, droë rooi- en laatoeswyne. Die gemiddelde gliserolvlakke in die witwyne was heelwat laer as die gemidelde gliserolvlakke in die droë rooiwyne (6.82 gIL teenoor 10.49 gIL, onderskeidelik). Geen beduidende verwantskap kon aangetoon word tussen die gliserolkonsentrasie in die wyn en die geografiese oorsprong, oesjaar, en die gisras wat gebruik is in die produksie van die wyn nie. Die kwaliteit van rooiwyn kon nie beduidend met die gliserolkonsentrasie geassosieer word nie. In die geval van wit wyn was die verwantskap statisties beduidend, maar die verskille was klein en moontlik nie van veel praktiese waarde nie. Die aktualiteit van gliserol vir die moderne Suid-Afrikaanse wynmaker is geëvalueer op grond van die opinies van In paneel van 15 Suid-Afrikaanse kundiges, rakende aspekte wat verband hou met die algemene opvattings oor gliserol en wyn. Die paneel het bestaan uit wynmakers, wynkundiges en chemici. Die opinie van die panel is deur middel van "n vraelys bekom en is vervat in "n kwalitatiewe databasis. Die resultate van hierdie menigspeiling het getoon dat gliserol wel vir die Suid- Afrikaanse wynmakers belangrik is en dit het ook die behoefte uitgewys vir die ontwikkeling en optimisering van metodes wat geskik is vir die roetine analyses van gliserol in wyn. Die invloed van gliserol op die vlugtigheid van "n seleksie van hoëralkohole en esters is ondersoek in "n model wyn sowel as "n wit wyn, waarvan die basiese gliserolkonsentrasie 5.4 gIL was. Soliede-fase mikroekstraksie van die gasfase van wyn is opgevolg met "n gaschromatografiese analise. Resultate het getoon dat "n stapsgewyse toename in die gliserol konsentrasie, oor "n konsentrasie reeks van 0 - 10 gIL in die model wyn, en 0 - 15 gIL in die wit wyn, nie gepaard gegaan het met "n reglynige toename of afname in die konsentrasie van die aromakomponente nie. Vir al die komponente wat ondersoek is, was die samestelling van die gasfase in monsters wat die laagste gliserol konsentrasie gehad het, teenoor dié wat die hoogste gliserol konsentrasie gehad het, nie beduidend nie. Nietemin het die resultate getoon dat gliserol wel "n effek het op die vlugtigheid van die aroma komponente wat in hierdie ondersoek gebruik is, maar dat die aard van die effek kompleks en nie-liniê is. Fourier-transformasie-infrarooispektroskopie (FT-IR) is gebruik om die metodes vir die analise van gliserol in wyn sodanig te optimiser, dat vinnige en akkurate bepalings op "n roetine basis in wyn gedoen kan word. Kalibrasies is ontwikkel vir die kwantifisering van gliserol in droëwyn en laatoeswyn. Die standaard voorspellingsfout van die kalibrasies wat ontwikkel is, was 0.38 gIL in droëwyn en 0.65 gIL in die geval van laatoeswyn. Inherente variasie in die FT-IR-spektra word deur eksterne faktore soos die proses tegnologie wat gebruik is om die wyn te berei, die kultivar en geografiese oorsprong van die wyn veroorsaak en hierdie variasie kan "n effek hê op die voorspelingsakkuraatheid van FT-IR spektroskopie. Om die effek van hierdie variasie op die akkuraarheid van die analitiese data te evalueer, is die voorspelling van gliserol as modelsisteem gebruik. Hoofkomponentanalise van die FT-IR spektra is gedoen om dié wyne met onnatuurlike FT-IR-spektra te identifiseer, ten einde beheer oor die akkuraatheid van die analitiese data uit te oefen. "n Verdere model wat ook gebaseer is op hoofkomponentanalise van die FT-IR-wynspektra is ontwikkel vir die interpretasie en klassifikasie van wynmonsters met onnatuurlike FT-IRspektra. Met die model wat ontwikkel is kon onnatuurlike wynmonsters met "n akkuraatheid van 100% gëidentifiseer word. Hierdie werk vorm die basis waarop kwaliteitsbeheer verder uitgebrei kan word sodat wyne met onnatuurlike spektra gëidentifiseer kan word, sowel as om te verseker dat akkurate data gegenereer word as FT-IR as analitiese metode gebruik word vir die kwantifisering van gliserol in wyn. FT-IR spektroskopie is ook gebruik om "n vinnige skandeerproses te ontwikkel waarmee die fermentasieprofiele van wyngiste geëvalueer kan word. Die seleksie giste wat vir hierdie doel gebruik is, sluit kommersiële Suid-Afrikaanse wyngiste in, sowel as hibriede Saccharomyces cerevisia-giste wat normaalweg hoër vlakke van gliserol tydens die fermentasieproses produseer. Kalibrasies is ontwikkel vir die akkurate kwantifisering van gliserol, vlugtige suur, alkohol, reduserende suiker en glukose, in Chenin blanc-mos sowel as in 'n sintetiese medium. Hierdie werk vorm die basis waarop verdere uitbreidings gedoen kan word, sodat meer metaboliete gemeet kan word en 'n groter verskeidenheid van fermentasiemedia gebruik kan word. Hierdie ontwikkeling is waardevol vir toekomstige toepassings in die navorsings- sowel as die industriële omgewing. Die metode wat ontwikkel is illustreer ook hoe hierdie toepassing 'n ondersteunende rol kan speel in wyngisontwikkelingsprogramme deur die aanvanklike evalueringsproses van die giste te versnel.

Thesis (MSc)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Nitrogen composition of grape must is highly variable and impacts on the health of the fermenting yeast population as well as the formation of aroma and flavour compounds in wine. Insufficient yeast assimilable nitrogen (YAN), mostly consisting of amino acids and ammonium, can lead to stuck or sluggish fermentations as well as the formation of undesirable compounds such as H2S. Furthermore, it is well established that the total concentration of YAN and the specific amino acid composition have a significant impact on the final aroma and flavour of wines. However, the impact of individual amino acids and of specific amino acid compositions on fermentation kinetics and on the production of aroma and flavour impact compounds under winemaking conditions is not well understood. The first goal of this study was to evaluate the effect of single amino acids on growth kinetics and major volatile production of two industrial wine yeast strains under conditions resembling wine fermentations. To facilitate these fermentation conditions while also allowing for easy reproducibility and manipulation of the initial components, a synthetic grape media was utilized. Biomass formation, exponential growth rate, lag phase, and fermentation duration were utilized to evaluate the efficiency of single amino acids. The data show that previously observed trends in laboratory strains mostly apply to these conditions and strains. In general, the efficiency of amino acids to be used as nitrogen sources and the production of major volatiles due to their presence followed the same patterns for both industrial yeast strains. However, the production of the secondary metabolites butanol, propanol, acetic acid, and ethyl acetate were found to be produced in different final concentrations dependent upon the yeast strain. The branched-chained and aromatic amino acids (BCAAs) treatments were observed to have the most dramatic effects on major volatile production. Investigating the relationships between the initial concentration of the BCAAs and the final concentrations of major volatile compounds, it was found that the production of fusel alcohols and fusel acids due to the degradation of BCAAs by S. cerevisiae could be predicted from the initial concentration of BCAAs. While under simple nitrogen conditions the production of several other secondary metabolites such as butanol, propionic acid, valeric acid, decanoic acid and 2-phenylethyl acetate were found to be correlated to the initial concentration of BCAAs in the media. Future studies should focus on the validation of these trends in aroma production in real grape musts under various fermentation temperatures for a number of industrial wine yeast strains.
AFRIKAANSE OPSOMMING: Die stikstof samestelling van druiwemos is hoogs veranderlik en impakteer op die kerngesondheid van die fermenterende gis populasie asook die produksie van aroma- en geurverbindings in wyn. Onvoldoende assimileerbare stikstof (ook genoem “yeast assimilable nitrogen” (YAN)), wat meestal bestaan uit aminosure en ammonium, kan aanleiding gee tot steek- of slepende fermentasies, asook die vorming van ongewensde verbindings soos H2S. Dit is alombekend dat die totale konsentrasie van YAN en dan ook die spesifieke aminosuur samestelling ‘n noemenswaardige impak op die finale aroma en smaak van wyn het. Die invloed van individuele am inosure en spesifieke aminosuur samestellings op die fermentasie kinetika, asook die produksie van verbindings met ‘n impak op die wyn aroma en smaak, word egter nie deeglik verstaan nie. Die eerste doelwit van die studie was om twee industriële gisrasse te gebruik om die effek van enkel aminosure op die groei-kinetika en produksie van die vername vlugtige verbindings onder wynmaak toestande te bepaal. Kunsmatige, gedefinieerde druiwermosmedium is gebruik om wynmaak toestande te simuleer en ook herhaalbaarheid en manipulering van die aanvanklike samestelling van die medium te verseker. Die studie het vorige tendense wat opgemerk is in die evaluasie van laboratorium rasse onder soortgelyke toestande bevestig. Die doeltreffendheid waarmee aminosure oor die algemeen gebruik word as stikstofbron, asook die produksie van die vernaamste vlugtige verbindings wat gekoppel is aan hulle teenwoordigheid, het ‘n vergelykbare patroon vir beide rasse gevolg. Die sekondêre metaboliete butanol, propanol, asetaat en etiel-asetaat is egter wel in verskillende eindkonsentrasies geproduseer deur die verskillende gisrasse. Die vertakte-ketting en aromatiese aminosuur (“branched-chained and aromatic amino acids” (BCAAs)) behandelings het die mees dramatiese effek op die produksie van die vernaamste vlugtige komponente gehad. Ondersoek na die verwantskap tussen die aanvanklike konsentraies van die BCAAs en die finale konsentrasies van dié verbindings het aangedui dat die produksie van hoër alkohole en sure, as gevolg van die afbraak van BCAAs deur S. cerevisiae, met behulp van die aanvanklike konsentrasie van die BCAAs voorspel kon word. Terselfdertyd is gevind dat onder eenvoudige stikstoftoestande, verskeie ander sekondêre metaboliete soos butanol, propionaat, valeriaat, dekanoësuur en 2-fenieletielasetaat, gekorreleer kan word met die aanvanklike BCAAs in die media. Verdere studies moet poog om hierdie tendense ten opsigte van aromaproduksie te bevestig en wel deur gebruik te maak van ware druiwemos, verskeie fermentasietemperature, asook ’n verskeidenheid van wyngisrasse.

Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Spoilage, be it due to microbial actions, chemical reactions or both, poses a serious threat to the food and beverage industries. Not only can spoilage lead to great economic losses, but it can also cause industries to lose their competitive edge in the economic and consumer market. Considering all the modern technologies and the range of preservation techniques that are available, it is surprising that spoilage is still an economic problem. Wine spoilage due to unpalatable bitterness, and the role of lactic acid bacteria (LAB) in causing this bitterness, have received much attention over the years, but no definite understanding has yet emerged. The first objective of this study was to isolate, enumerate and identify the LAB from three red grape varieties, viz. Pinotage, Merlot and Cabernet Sauvignon. The LAB populations on the grapes of all three varieties ranged from 102 to 104 cfu/ml during the 2001 and 2002 harvest seasons. The Cabernet Sauvignon grapes had slightly higher numbers than the Pinotage and Merlot. The LAB population in the Cabernet Sauvignon, Pinotage and Merlot wines after completion of the alcoholic fermentation ranged from 102 to 105 cfu/ml, while during 2002 the numbers in wine undergoing malolactic fermentation (MLF) ranged from 104 to 108 cfu/ml. The isolated LAB were divided into the three metabolic groups, with 59% belonging to the facultatively heterofermentative group, 26% to the obligately heterofermentative group and 15% to the obligately homofermentative group. The isolates were identified by means of species-specific primers as Leuconostoc mesenteroides (4), Oenococcus oeni (28), Lactobacillus brevis (15), Lb. hilgardii (15), Lb. plantarum (98), Lb. pentosus (12), Lb. paraplantarum (3), Lb. paracasei (28), Pediococcus acidilactici (2) and Pediococcus spp. (35). The most predominant species isolated was Lb. plantarum, followed by Pediococcus spp. The results suggest that Pinotage carries a more diverse LAB population in comparison to Merlot and Cabernet Sauvignon. The second objective of this study was to determine the presence of the glycerol dehydratase gene in the LAB strains by using the G01 and G02 primers. Twenty-six strains tested positive, namely Lb. plantarum (15), Lb. pentosus (1), Lb. hilgardii (5), Lb. paracasei (2), Lb. brevis (2) and a Pediococcus spp. (1). Interestingly, 62% of these strains were isolated from Pinotage. The strains all had the ability to degrade glycerol by more than 90%, and no significant differences were observed between the species. The GO-possessing strains exhibited varying degrees of inhibition towards Gram-positive and Gram-negative bacteria, and the results suggest that this inhibition activity may be similar to that of reuterin, which is produced by Lb. reuteri. This study can form the foundation for unravelling the causes of bitterness in red wines. Combining the results of this study with analytical, sensory and molecular data may very well provide the industry with valuable tools with which to combat the occurrence of bitterness.
AFRIKAANSE OPSOMMING: Bederf as gevolg van mikrobiese aksies, chemiese reaksies of beide, hou 'n groot bedreiging vir die voedsel- en drankbedrywe in. Nie net kan bederf lei tot groot ekonomiese verliese nie, maar dit kan ook veroorsaak dat bedrywe hul kompeterende voordeel in die ekonomiese en verbruikersmarkte verloor. As die moderne tegnologie en die reeks preserveringstegnieke wat beskikbaar is, in ag geneem word, is dit verbasend dat bederf steeds 'n ekonomiese probleem is. Wynbederf as gevolg van oormatige bitterheid en die rol van melksuurbakterieë (MSB) in die ontwikkeling van hierdie bitterheid het oor die jare heen baie aandag geniet, maar geen definitiewe verklaring is nog daarvoor gevind nie. Die eerste doelwit van hierdie studie was om MSB vanaf drie rooidruifvariëteite, nl. Pinotage, Merlot en Cabernet Sauvignon, te isoleer, te kwantifiseer en te identifiseer. Die MSB-populasies op die druiwe van al drie variëteite het gedurende die 2001- en 2002-parsseisoene tussen 102 en 104 kvu/ml gevarieer. Die Cabernet Sauvignon-druiwe het effens hoër getalle as die Pinotage- en Merlot-druiwe gehad. Die MSB-populasies in die Cabernet Sauvignon-, Pinotage- en Merlot-wyne aan die einde van die alkoholiese fermentasie het tussen 102 en 1055 kvu/ml gevarieer. Gedurende 2002 het die MSB-getalle in die wyne waarin appelmelksuurgisting (AMG) aan die gang was tussen 104 en 108 kvu/ml gevarieer. Die geïsoleerde MSB was onderverdeel in die drie metaboliese groepe, met 59% wat behoort aan die fakultatiewe, heterofermentatiewe groep, 26% aan die obligate, heterofermentatiewe groep en 15% aan die obligate, homofermentatiewe groep. Die isolate is geïdentifiseer as Leuconostoc mesenteroides (4), Oenococcus oeni (28), Lactobacillus brevis (15), Lactobacillus hi/gardii (15, Lactobacillus p/antarum (98), Lactobacillus pentosus (12), Lactobacillus parap/antarum (3), Lactobacillus paracasei (28), Pediococcus acidi/actici (2) en Pediococcus spp. (35) deur middel van spes iespesifieke inleiers. Die mees algemeen geïsoleerde spesies was Lb. p/antarum, gevolg deur Pediococcus spp. Die resultate impliseer dat Pinotage 'n meer uiteenlopende MSB-populasie in vergelyking met Merlot en Cabernet Sauvignon dra. Die tweede doelwit van hierdie studie was om die teenwoordigheid van die gliseroldehidratase-geen in die MSB-isolate deur middel van die GD1- en GD2- inleiers te bepaal. Ses-en-twintig isolate was positief, nl. Lb. p/antarum (15), Lb. pentosus (1), Lb. hi/gard;; (5), Lb. paracasei (2), Lb. brevis (2) en 'n Pediococcus spp. (1). 'n Interessante resultaat was dat 62% van hierdie isolate vanaf Pinotage geïsoleer is. Die isolate was almal in staat om meer as 90% van die gliserol te gebruik en geen noemenswaardige verskille is tussen die isolate waargeneem nie. Die GD-bevattende isolate het verskillende grade van inhibisie teenoor Grampositiewe en Gram-negatiewe bakterieë getoon, en die resultate impliseer dat hierdie inhiberende aktiwiteit dieselfde is as dié van reuterin wat deur Lb. reuteri geproduseer word. Hierdie studie kan dus die basis vorm vir die ontrafeling van die oorsake van bitterheid in rooiwyne. Deur die resultate van hierdie studie met analitiese, sensoriese en molekulêre data te kombineer, kan die wynbedryf voorsien word van waardevolle metodes om die voorkoms van bitterheid mee te bekamp.

Los aromas se definen como productos no destinados al consumo como tales, que se añaden a los alimentos o a ciertos medicamentos para darles un olor o un sabor, o para enmascarar y/o modificar su olor o sabor. Debido a la naturaleza volátil de los aromas se suele recurrir a técnicas de encapsulación para reducir su evaporación y mejorar su vida media, así como también controlar su liberación. Esta última es una de las principales líneas de investigación que se está llevando a cabo en el sector de los aromas. Las técnicas de extrusión y lecho fluido son de uso común en la industria farmacéutica y su aplicación en la preparación de ingredientes alimentarios es de elevado interés competitivo para la industria alimentaria, debido a que permiten la obtención de formas multiparticulares de administración oral de liberación controlada. En concreto, la técnica de extrusión-esferonización permite la elaboración de pellets matriciales, de los cuales se han reportado varias ventajas en el campo farmacéutico y que podrían aplicarse en el campo de los aromas. Los pellets son formas multiparticulares libres de flujo con una distribución de partícula que típicamente varía entre 0,5-1,5 mm, cuya ventaja principal es que permiten controlar la velocidad de liberación de la sustancia vehiculizada, a través de dos formas diferentes: a) recubriendo los pellets con una película de un material que retenga al activo en su interior, retrasando así la liberación; y b) modificando el interior de los pellets mediante la adición de sustancias que influyan en su comportamiento. El objetivo de la presente tesis es efectuar el desarrollo de sistemas de vehiculización para aromas basados en tecnologías mixtas de extrusión y lecho fluido, con el fin de controlar temporalmente la liberación de los mismos, de manera que se pueda lograr modificar la percepción sensorial del consumidor. Para llevar a cabo este fin se investiga, por una parte, la vehiculización de aromas tanto simples (mentol y benzaldehído) como complejos (aroma de fresa y aroma de hierbabuena) en pellets matriciales que presentan una matriz compuesta por celulosa microcristalina como agente diluyente e hidroxipropilmetilcelulosa (HPMC) como agente aglutinante; y por otra parte, el efecto de otras sustancias modificadoras de la liberación en dicha matriz, tales como etilcelulosa, almidón pregelatinizado y HMPC de diferentes viscosidades (E6, K4M, K100M). Paralelamente, se estudia el recubrimiento pelicular de los pellets obtenidos mediante lecho fluido en condiciones óptimas de preservación de los aromas que vehiculizan. Asimismo, se estudia estrategias de microencapsulación para mejorar la estabilidad de los aromas líquidos previo proceso de extrusión. A partir de los resultados obtenidos se eligen las mejores formulaciones para caracterizarlas mediante la metodología SeDeM; analizarlas mediante cromatografía de gases con un método analítico validado; aplicarlas en goma de mascar y evaluarlas a nivel sensorial para determinar la percepción sensorial provocada en el consumidor. Los resultados demuestran que es posible obtener una plataforma de formulaciones de composición sencilla y versátil, que permiten vehiculizar aromas tanto simples como complejos, tanto sólidos como líquidos, con una carga hasta 50 % p/p con respecto a peso seco para los aromas sólidos y hasta 30 % p/p con respecto a peso seco para los aromas líquidos. Así mismo, el recubrimiento pelicular permite controlar temporalmente la liberación del aroma vehiculizado. La presente investigación desarrollada ha dado lugar a una patente registrada en la Oficina Española de Patentes y Marcas.
Flavours are defined as products not intended for consumption as such, which are added to foods or certain medicines to give them an odour or flavour, or to mask and/or modify their odour or flavour. Due to the volatile nature of flavours, encapsulation techniques are often used to reduce their evaporation and improve their half-life, as well as to control their release. Extrusion and fluid bed techniques are commonly used in the pharmaceutical industry and their application in the preparation of food ingredients is of highly competitive interest for the food industry, since they allow obtaining multi-particulate forms of oral administration of controlled release. Specifically, the extrusion-spheronisation technique allows the production of matrix pellets, whose several advantages have been reported in the pharmaceutical field, that could be applied in the field of flavours. The main advantage of pellets is allowing to control the release rate of the vehiculised substance in two different ways: a) coating the pellets with a film of a material that retains the active ingredient inside of them, thus delaying the release rate; and b) modifying the interior of the pellets by adding substances that influence their behaviour. The objective of this thesis is to perform the development of vehiculisation systems for flavours, based on mixed extrusion and fluid bed technologies, in order to temporarily control release, so that the sensory perception of the consumer can be modified. In order to accomplish this aim, on one hand, the vehiculisation of both simple (menthol and benzaldehyde) and complex flavours (strawberry flavour and peppermint flavour) is investigated in matrix pellets that present a matrix composed of microcrystalline cellulose, as a diluent agent, and hydroxypropyl methylcellulose (HPMC), as a binding agent; on another hand, the effect of other release modifying substances on the matrix is evaluated, such as ethylcellulose, pregelatinized starch and HMPC of different viscosities (E6, K4M, K100M). At the same time, the film coating of the pellets by fluid bed technique under optimal conditions of preservation of the flavours they vehiculise, is studied. Moreover, microencapsulation strategies are studied to improve the stability of liquid flavours before the extrusion process. The best formulations of the aforementioned studies are characterised using the SeDeM methodology, analysed by gas chromatography with a validated analytical method, applied in chewing gum and evaluated at the sensory level to determine the sensory perception caused in the consumer. The research has led to a patent registered at the Spanish Patent and Trademark Office.

Afin de rendre les régimes alimentaires occidentaux plus durables, un changement d’alimentation s’impose. Parmi les sources végétales prometteuses, la fèverole (Vicia faba L.) peut être utilisée comme ingrédient à fort potentiel nutritionnel et fonctionnel dans la formulation de produits alimentaires. Les graines de fèveroles sont transformées en ingrédients, qui peuvent à leur tour être modifiés, fonctionnalisés, afin d’être plus adaptés à des applications alimentaires. Ce travail de thèse avait pour objectif de comprendre le rôle des conditions de transformation des ingrédients riches en protéines de fèveroles sur leurs propriétés fonctionnelles et leur flaveur. L’impact des conditions de transformation, choisies pour être réalistes sur le plan industriel, a été étudié en utilisant une approche multi-dimensionnelle et trouver ainsi un compromis favorable à l’expression des propriétés des différents ingrédients. Plus précisément, un concentrât de fèveroles riche en protéines, traité selon un procédé de transformation doux à l’échelle industrielle, a été sélectionné puis modifié par différentes conditions de transformation, i.e. le pH (2, 4, 6,4 et 11), la température (55, 75 et 95 °C) et la durée du traitement (30 et 360 min). Trente-six ingrédients différents ont ainsi été produits. Ceux-ci ont ensuite été utilisés à deux pH différents, 4 et 7, dans des systèmes modèles proches d’applications de type boissons. Au cours de l'utilisation de ces ingrédients, la fonctionnalité des boissons (propriétés moussantes et émulsifiantes), la perception olfactive des produits et la composition en composés volatils et non volatils ont été étudiées. Les résultats montrent que les conditions de transformation sont capables de moduler les propriétés fonctionnelles et olfactives du concentrât de fèveroles, l’analyse étant renforcée par le biais de différents modèles statistiques. Les propriétés des mousses et des émulsions sont principalement gouvernées par le pH d'utilisation des ingrédients. Un pH proche du point isoélectrique des protéines de fèverole (pH 4) n'est pas favorable ni à la stabilité de la mousse, ni à la capacité d’émulsification ou à la stabilité de l'émulsion. Des corrélations entre les propriétés fonctionnelles et les propriétés physico-chimiques ont été mises en évidence et s’expliquent par les propriétés des protéines. Par ailleurs, la flaveur est fortement influencée par les conditions de modification et d'utilisation des ingrédients, en particulier par le pH. Selon les modifications du concentrât initial, en conditions douces ou sévères, la perception peut être modifiée, pour évoluer d’odeurs vertes à des odeurs cuites, tandis que les conditions d'utilisation des ingrédients (pH) peuvent conduire à des perceptions « douces » ou rances. La composition en composés volatiles de l’espace de tête des ingrédients mis en suspension montre la présence de nombreux aldéhydes et alcools. L'oxydation des lipides apparaît importante dans la génération de composés volatiles, de même que des réactions de dégradation des protéines, des sucres et des caroténoïdes. Les propriétés physico-chimiques et sensorielles des composés à l’origine du potentiel antioxydant, du goût (amertume et astringence), de la couleur et des effets antinutritionnels ont également été étudiés. Les composés phénoliques et les saponines se sont avérés significativement impactés par les conditions de transformation mises en œuvre lors de la modification des ingrédients, en particulier par le pH. Les profils en composés phénoliques et en saponines obtenus à l’issue des traitements acide et alcalin (pH 2, 4 et 11) apparaissent ainsi très distincts de celui obtenu par un traitement effectué sans ajustement de pH (pH 6,4). Des études complémentaires menées à pH 6,4 indiquent que cette différence serait liée à une question d’extractibilité variable des composés étudiés et/ou à une réactivité plus ou moins élevée selon les conditions de transformation
The growing population is demanding new healthy, sustainable solutions for foods and beverages. Fava bean (Vicia faba L.) is a promising plant source that can provide nutritional and functional ingredients for different food applications. Fava bean is processed to form ingredients and they can be further modified to render them fit for food applications. This PhD work aimed to understand the role of processing conditions on functional and flavor properties, and apply this understanding to produce and use fava bean protein-rich ingredients. It investigated the effects of certain industrially relevant process conditions using a cross-dimensional approach to find the right kind of compromise between different ingredients properties. To be precise, a very gently processed fava bean protein rich concentrate was industrially procured, which was then modified by process conditions such as pH (2, 4, 6.4 and 11), temperature (55, 75 and 95 °C) and treatment duration (30 and 360 min) to produce 36 different ingredients. These were further utilized at two pH (4 and 7) in systems close to beverage applications. During ingredient utilization, beverage functionalities (foam and emulsion) along with odor perception and non-volatile compounds were investigated for all ingredients as a function of process conditions.Results showed that process conditions were able to drive functional and flavor properties of the fava bean concentrate, strengthened by different statistical models. Foam and emulsion properties were predominantly governed by the pH during ingredient utilization. In general, utilization pH around the isoelectric point of fava proteins (pH 4) was not suitable for foam stability, emulsion capacity nor emulsion stability. Strong correlations between functional and physico-chemical properties were identified and explained by protein properties. In addition, flavor was heavily driven by the modification and utilization conditions, especially the pH.From gentler to vigorous process conditions, perception can be modified from more green to more cooked flavors, whereas different conditions of application (e.g. pH) can modulate between “sweet” and rancid perceptions. Considering volatiles composition, aldehyde signals were primarily detected in ingredient suspensions head-space. But furanoids, terpenoids, alcohols and ketones signals had the next higher contribution for modifications at pH2, 4, 6.4 and 11 respectively. Lipid oxidation was deemed important in generating volatiles, along with other reactions including proteins, sugars and carotenoids degradation. Going deeper into understanding of physico-chemical and sensory properties, determinants of antioxidant potential, taste (bitterness and astringency), color and even anti-nutritional effects were also investigated. Phenolic compounds (flavan-3-ols, flavones, flavonols, hydroxycinnamic acids) and saponins were significantly impacted by process conditions during ingredient modification, especially by pH. For phenolic compounds, acidic and alkaline conditions (pH 2, 4 and 11) were highly distinct compared to the non-pH adjusted process (pH 6.4) in changing the phenolic and saponin profiles of the ingredients. When looked closely at non-pH adjusted processes, their variability due to increasing degree of processing seemed to be either a function of their variable extractability and/ or their reactions involving their structural rearrangement.Thus, process conditions played an important role in fava bean ingredient properties, and this work opens up new arena for inter-disciplinary study based on nutritional (anti-oxidant and anti-nutritional aspects), sustainability (life cycle assessment), functionality (gelation) and sensory (texture, sweetness, bitterness) considerations of fava bean as potential ingredients for industrial food applications

Staling in beer is inevitable. Oxidation and increased temperatures are the main causes of stale flavors in bottled beers. Since 1934, research has been done to identify compounds and pathways involved in creating stale flavors. Although many research papers report stale flavors, there is not a lexicon per se of stale aromas for North American lagers. This study has been divided into two parts, 1) the process of developing a lexicon for stale aromas for North American lagers and its application, and 2) the use of a consumer panel to determine whether the North American lager consumer has a preference for aged versus fresh beer and whether the consumer could perceive a difference between the two. In the first study, three brands of North American lagers were aged in 27°C storage for three months and 38°C storage for two weeks. A lexicon for staling aroma for North American lagers was created, using a trained descriptive panel. The lexicon had two tiers; the first tier had five descriptors that were category headings for the second tier of descriptors. Panelists were instructed to rate the first tier descriptors, but using the descriptors in the second tier was optional. To validate the lexicon, descriptive analysis was performed on the stored samples. The data were analyzed using principal components analysis (PCA) for the first tier descriptors and generalized procrustes analysis (GPA) for the second tier descriptors. The lexicon was used successfully, characterizing the control beers as sulfury and fruity and the aged beers as sweet brown. Within the sulfury category, panelists described control beers with the attributes perm solution and skunky. Within the sweet brown category, panelists described the aged beers with the descriptors baked pineapple and honey. The beers stored at different storage temperatures behaved differently across time. The maps constructed with PCA and GPA show a tendency for control samples to start out sulfury and, through time, age with sweet brown characteristics. In the second study, a consumer panel was implemented to 1) determine if the average North American lager consumer had a preference for fresh versus stored beer, and 2) to determine if perceivable differences existed between the fresh versus stored samples. A consumer test was designed using the three North American lagers that were tested in the trained panel. The target number of consumers for each brand was 100. The aged beer was stored at 38°C for 1 and 2 weeks, and the control was stored at 1°C for that time period. A preference test, followed by a triangle test, was performed on control versus 1 week at 38°C and control versus 2 week at 38°C for each brand (2 preference and 2 triangle tests for each brand; control versus 1 week and control versus 2 weeks). The results showed no significant preference for any brand/time point. Brand A had the only significant difference (p <0.05) between samples stored at 38°C for 2 weeks and the control (The results showed no preference). Additional research must be done for more conclusive information, but this research shows that a small group of North American lager consumers do not have a preference between aged beer and fresh beer and, for the most part, cannot tell a difference between aged beer and fresh beer.
Graduation date: 2002

Sensory evaluation and instrumental methods were applied to the evaluation of strawberry juice concentrate (68°Brix) stored at 20°C which had been produced both commercially (C-SJC) and in a pilot plant (SJC). Sensory evaluation included taste and aroma ratings by intensity scaling and time-intensity of taste, and visual colorimetry by matching Munsell color chips. Instrumental analyses included tristimulus colorimetry (i.e. Hunter colorimeter), spectrophotometric colorimetry for pigment analyses, titrametric analyses for acidity (pH and titratable acidity) and free α-amino acids (formol number), and headspace gas analyses for CO₂ and O₂. During six days storage of C-SJC, a decrease in concentration of anthocyanins and increase in polyphenolics (tannin) was associated with an increase in astringency. Free α-amino acids were observed to decrease, while CO₂ was released. These changes were associated with an increase in musty/moldy and pungent aromas. Free sugars and titratable acidity did not change. The pilot plant SJC was processed from blanched and unblanched fruit to evaluate the relative importance of oxidase activity (i.e. polyphenoloxidase) prior to pasteurization. The blanching treatment increased the astringency and sourness in unstored SJC. These affects were associated with an increase in concentration of polyphenolics (tannin). During storage, the blanch treatment decreased the rate of anthocyanin loss and decreased the release rate of CO₂, yet degradation rates were still high. The 0₂ concentration in headspace did not change significantly during storage indicating that polyphenoloxidase (PPO) activity during storage was low. The musty/moldy and pungent aromas increased similarly to C-SJC. A chemical mechanism accounting for these changes is proposed where products from the oxidative degradation of ascorbic acid contribute directly or indirectly to the degradation of anthocyanins to yield browning. Further, high initial concentrations and subsequent decreases during C-SJC storage of free α-amino acids indicate that Strecker degradation is a participating mechanism. Associations of browning with the development of off-flavors suggest this chemical mechanism forms odor-active volatile compounds.
Graduation date: 1989

Malt, wort and beer samples representing a single pilot brew were extracted from Celite columns with Freon 114. Total extracts were analyzed by gas chromatography/mass spectrometry. Compounds were identified that were unique or common to beer, wort or malt and quantities present were determined for those common to the three sample types. Concentrated extracts were separated by liquid chromatography on partially deactivated silica gel packed in Teflon tubes, using Freon 11 as the solvent. Fractions from liquid chromatography were analyzed by descriptive sensory evaluation. Those fractions selected as bearing cereal-like, grassy, nutty or malty aroma characteristics were analyzed by gas chromatography. Freon extracts and fractions were found suitable for descriptive sensory evaluation and this was used to advantage in locating fractions with the desired aroma characteristics. Cereal-like, grassy, nutty or malty aroma characters were associated with liquid chromatographic fractions containing primarily alcohols, aldehydes and ketones. The Ascending Method of Limits for determination of the threshold of added substances in beer was critically reviewed and a new threshold test was developed. The new test design reduces the sample requirement from eighteen to twelve for each session. In contrast to the Ascending Method of Limits, the new test design was amenable to statistical evaluation and statement of a level of confidence for the threshold intervals determined. Both a nine-point intensity scale of difference from the labeled reference and a category scale were applied to the new test design. Intensity scale data were normalized and subjected to analysis of variance and a series of one-sided t-tests to determine individual and combined panel threshold intervals. Category scale data were analyzed by a rank sums test to determine individual thresholds and the R-index values thus obtained were subjected to analysis of variance and orthogonal contrasts of means to establish the combined panel threshold. The intensity scale method applied to the new test design provided the lowest and narrowest estimates of the threshold interval in comparative testing with the category scale method and the Ascending Method of Limits and, in addition, required fewer replications than the category scale method to establish the threshold interval.
Graduation date: 1989

Response Surface Methodology (RSM) was used to study the effect of two variables, sugar level (12-16 °Brix) and acid level (0.3-0.7 % T.A.) on sensory qualities and desirability of blackberry juice drinks. Three blackberry juice levels (10%, 15%, and 20%) were used to study the influence of juice flavor on sensory qualities and desirability of the juice drinks. A trained panel evaluated three attributes, blackberry flavor, sweetness, and sourness intensities, of the juice drinks. The consumer panel gave desirability and three attributes just-right ratings. A Balanced Complete Block Design was used. Blackberry flavor intensity was enhanced by sugar level. Blackberry flavor intensity was enhanced by acid level to a point about 0.5% T.A., and then decreased. Blackberry flavor intensity was not related to °Brix:acid ratio and was only related to the sweetness:sourness ratio at the 20% juice level. Sweetness and sourness intensities increased with increasing sugar and acid levels. There was a suppression effect of sugar and acid on each other in the juice drink. The relationships of sweetness, sourness, and sweetness:sourness ratios to °Brix:acid ratios were all linear. Desirability rating was related to °Brix:acid and sweetness:sourness ratios for the 10% and 20% juice levels, for 15% juice level no association was found. The formula which received the closest to "just right" ratings and highest overall desirability rating had in a °Brix of 15.4 and a % titratable acidity of 0.64, resulting in a °Brix:acid ratio of 24 and a corresponding sweetness:sourness ratio of slightly less than 1.0. In general, the 15% juice level was the best because of its sugar and acid tolerance and high desirability.
Graduation date: 1989

Fresh ripe, cantaloupes were processed into juice and juice concentrate. Processing trials were conducted on fresh and frozen fruits with and without rind. The effects of maceration enzymes and fining agents on yield and quality were investigated. Compositional measurement included °Brix, pH, titratable acidity, formol values, ascorbic acid content, total carotenoids, sugar and nonvolatile acid profiles, browning indices and Hunter color parameters. Considerable ascorbic acid degradation occurred during processing. The high juice yield (80%) and low acidity suggest its potential use as an alternate sweetener source. Sensory evaluation by a trained panel showed that concentrating the juice samples from flesh and rind can remove the rind aroma and flavor characteristics. Juices obtained from flesh and from flesh and rind were not significantly different (p [less than or equal to] 0.05) except for overall intensity and fresh fruit flavor characters. Single strength juice was significantly different (p [less than or equal to] 0.05) from concentrate on most aroma and flavor characters.
Graduation date: 1991

'Marion' and 'Thornless Evergreen' blackberry volatiles were analyzed by capillary gas chromatography-flame ionization detection (GC-FED) and GC-mass spectrometry (GC-MS). Based on total percentage of FID area 'Thornless Evergreen' contains significantly more alcohols, hydrocarbons, and phenols than the 'Marion'; 'Marion' contains more acids and esters. Both cultivars contained comparable amounts of aldehydes and ketones; alcohols were most abundant. The six most abundant volatiles in 'Marion' were ethanol, acetic acid, hexanoic acid, ethyl acetate, linalool, and 2-heptanol; they totaled 52% of total peak area. In 'Thornless Evergreen' the six most abundant volatiles were 2-heptanol, ethanol, 2,3-butanediol, hexanol, α-pinene, and ethyl acetate; they totaled 43% of total peak area. 'Marion' and 'Thornless Evergreen' blackberry aromas were compared using a pair of extraction and gas chromatography-olfactometry-mass spectrometry (GC-O-MS) methods. One method is based on purge-and-trap (P&T, dynamic headspace) extraction and aroma intensity rating by detection frequency (DetF) and a numeric scale, and the other based on solvent assisted flavor extraction (SAFE) and aroma threshold dilution analysis (AEDA). The parallel use of P&T-DetF GC-0 and SAFE-AEDA provided more representative blackberry volatile compositional data than either alone. Eighty-four compounds were identified; seventy-seven were in 'Marion', and sixty-eight in 'Thornless Evergreen'. Thirty-seven have not been previously reported in blackberry. Fourteen volatiles out of eighty-four were described with aroma descriptors specific to bramble fruit (berry, blackberry, bramble, raspberry); no single compound was unanimously described as "characteristically blackberry". Fresh 'Marion' blackberry aroma has been described as floral, fruity, sweet, caramel-fruity, and woody, while fresh 'Thornless Evergreen' aroma is spicy, green, herbaceous, fruity, and sweet. Except for esters, the cultivars contain comparable numbers of acids, alcohols, aldehydes, furanones, hydrocarbons, ketones, phenolics, sulfur, and Theaspirane compounds. Research data implies some portion of the more floral, fruity, and sweet aroma of the 'Marion' blackberry may be the result of additional esters not shared with the 'Thornless Evergreen' blackberry, yet both cultivars apparently contain five furanones, which are powerful sources of sweet, fruity, and spicy aromas. Aroma reconstitution studies will be the key to resolving the significant aroma profile differences between 'Marion' and 'Thornless Evergreen' blackberries, as characteristic blackberry aroma is apparently a complex formulation of volatiles.
Graduation date: 2004