Tesis sobre el tema "Fermentation of foods"
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Xing, Huajing. "Impact of thiamine and pyridoxine on alcoholic fermentations of synthetic grape juice". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Summer2007/h_xing_072607.pdf.
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Adang, Arief. "Tape ketela (Indonesian fermented cooked cassava) fermentation". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302960.
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Yusof, Rokiah Binti Mohd. "Improved safety of infant weaning foods through lactic acid fermentation". Thesis, University of Surrey, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359907.
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Kateu, Kepher Kuchana, of Western Sydney Hawkesbury University, Faculty of Science and Technology y Centre for Advanced Food Research. "A study of traditional production of Ugandan fermented cereal beverage, Obushera". THESIS_FST_CAFR_Kateu_K.xml, 1998. http://handle.uws.edu.au:8081/1959.7/634.
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The study presented here was to investigate the traditional production of the Ugandan fermented cereal beverage, Obushera. The effects of germination and malting of sorghum grains under different steeping treatment were first investigated. The traditional preparation of Obushera beverage was carried out and course of fermentation monitored. The viscosity of Obushera was very low throughout the fermentation process. The microflora responsible for the fermentation of Obushera were identified. After considerable research and conduction of tests were carried out, it was found that there was no detectable quantity of alcohol in Obushera. It was also confirmed that that there were no strains of alcohol producing yeasts, such as Saccharomyces sp. found in the Obushera.Master of Science (Hons) (Food Science)
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Kateu, Kepher Kuchana. "A study of traditional production of Ugandan fermented cereal beverage, Obushera". Thesis, View thesis, 1998. http://handle.uws.edu.au:8081/1959.7/634.
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The study presented here was to investigate the traditional production of the Ugandan fermented cereal beverage, Obushera. The effects of germination and malting of sorghum grains under different steeping treatment were first investigated. The traditional preparation of Obushera beverage was carried out and course of fermentation monitored. The viscosity of Obushera was very low throughout the fermentation process. The microflora responsible for the fermentation of Obushera were identified. After considerable research and conduction of tests were carried out, it was found that there was no detectable quantity of alcohol in Obushera. It was also confirmed that that there were no strains of alcohol producing yeasts, such as Saccharomyces sp. found in the Obushera.
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Minchul, Gim. "Isolation and Identification of Lactic Acid Bacteria from Swedish Foods". Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-45774.
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Food fermentation is a method widely used in the past to extend the storage life of food. Numerous studies on fermented food have revealed that they not only have biopreservative properties but also health benefits. Lactic acid bacteria are the major group of microorganisms involved in food fermentation and the properties that influence food are primarily due to the compounds released from microorganisms such as organic acids and bacteriocins. Their health benefits are exerted through several mechanisms including inhibiting the growth of pathogenic bacteria and modifying the host immune response. A number of strains that have been investigated show different properties even between the same species thus emphasizing the importance of strain identification. To determine if some traditional fermented Swedish foods contain lactic acid bacteria, bacteria from four fermented Swedish foods (two surströmming and two sausages) were isolated using MRS broth. Bacterial isolates were examined for their colony and cell morphology and Gram staining and were found to be predominantly Gram-positive cocci or rods. 16S rRNA PCR amplifications of selected isolates was performed using universal prokaryotic primers and sequenced. The sequencing results showed that the bacterial isolates from Oskars surströmming Filéer and Gognacs medvurst were Lactobacillus sakei and the isolate from Mannerströms surströmming was Enterococcus sp. This study showed that the traditional Swedish fermented food evaluated did contain lactic acid bacteria.
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Kateu, Kepher Kuchana. "A study of traditional production of Ugandan fermented cereal beverage, obushera /". View thesis, 1998. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20040916.152810/index.html.
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Thesis (M.Sc.)(Hons)--University of Western Sydney, Hawkesbury,1998."Thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science (Honours) in Food Science." Includes bibliographical references.
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Altıok, Duygu Tokatlı Figen. "Kinetic modelling of lactic acid production from whey/". [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/gidamuh/T000471.pdf.
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Boualapha, Chanthilath Visith Chavasit. "Iodine stability and sensory quality of fermented fish and fish sauce fermented by using iodated salt /". Abstract, 2008. http://mulinet3.li.mahidol.ac.th/thesis/2551/cd412/4838150.pdf.
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Khem, Sarim. "Development of model fermented fish sausage from New Zealand marine species". Click here to access this resource online, 2009. http://hdl.handle.net/10292/807.
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Three New Zealand marine species, hoki (Macruronus novaezealandiae), kahawai (Arripis trutta) and trevally (Pseudocaranx dentex) were used to develop model fermented fish sausage. The formulation comprised fish mince, carbohydrate, minced garlic and salt in a mass ratio of 1 (fish): 0.15: 0.05: 0.03, respectively. The carbohydrate source was cooked rice or glucose. (Endogenous lactic acid bacteria (LAB) failed to ferment rice). Folate was also added to the mixture as a factor. The mixtures were extruded into 50 mL plastic syringes, where the needle end of the barrel had been excised by lathe. The lubricated barrel was overfilled to 60 mL, capped with a layer of ParafilmTM and aluminium foil, sealed tightly by rubber band and incubated at 30°C. Over time the piston was progressively advanced to yield samples for microbiological, physical, and chemical analysis. Over 96 hours an increase in the LAB count was observed with a concomitant decrease in pH. After fermentation was complete, the samples contained around 8.77 log cfu LAB g-1 with the pH range from 4.38 to 5.08. The microbiological and pH behaviour of each species varied between preparations. Hardness, adhesiveness, springiness and cohesiveness of the treatments increased with fermentation, except for hoki. The treatments showed different colour characteristics with fermentation. The light reflectance (L* values) of the trevally and kahawai treatments increased, while the a* (redness) and b* (yellowness) values decreased. Hoki exhibited smaller colour changes except for yellowness, which increased markedly. Proteolysis, measured colorimetrically by soluble peptide bonds, was greatest for trevally. Lipid oxidation, measured by the thiobarbituric acid method, was least for hoki, notably the species with the lowest fat content. Biogenic amines, which are a general quality indicator of fermented products, increased during fermentation. The trevally treatment generated the highest concentration of amines, but these values were lower than those reported for fermented fish sausage in Southeast Asia. Notably there were no important difference between folate treatments and those without folate. The results point to commercial opportunities and further research with New Zealand marine species, especially trevally. To improve the product quality and to show geographical exclusivity, further research could be done by using starter culture, and a New Zealand staple carbohydrate source such as kumara and potato, and spices and herbs which are commonly used in New Zealand, such as rosemary, thyme and sage or specific to New Zealand, such as horopito. In addition, sensory studies should also be performed before the products could be tested in the market.
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Hanisi, Nosipho. "Nguni fermented foods: working with indigenous knowledge in the Life Sciences: a case study". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1008372.
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This study examines learning interactions around indigenous ways of knowing associated with fermented grain foods (the making of umqombothi) and the concept of alcoholic fermentation in the Grade 11 Life Sciences curriculum. As an environmental education study it also investigates the cultural significances of the fermented grain food and how learners might make better lifestyle choices. The inclusion of indigenous ways of knowing in the Life Sciences curriculum (FET band) created spaces and opportunities for the use of both knowledge's in sociocultural context and the structured propositions of the learning area in order to construct knowledge. This stimulated learners' understanding of fermentation and also led to a valuing of social context as well as the cultural capital embedded in the indigenous ways of knowing. The study suggests that parental involvement contributed to this valuing of intergenerational ways of knowing. Learners also deliberated how colonial interpretations of Nguni culture and the religious beliefs of Christians had served to marginalise and foster a widening urban rejection of isiXhosa cultural practices related to fermented foods. In their learning and discussion, learners developed new insights and respect for isiXhosa fermentation practices (ukudidiyela) that bring out the food value and nutrition in the grain. The data illustrates that lesson activity that drew on relevant Learning Outcomes and Assessment Standards to integrate Indigenous Knowledge practices in a Life Sciences learning programme, served to enhance learner understanding of alcoholic fermentation. They also document a revaluing of cultural heritage and learners bringing up the problem of alcohol abuse in the community. Curriculum work with Indigenous Knowledge thus not only assisted learners to grasp the science but to use this alongside a valued cultural knowledge capital to deliberate and act on a local concern.
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Damin, Maria Regina. "Efeito da suplementação do leite com hidrolisado de caseína e com proteína concentrada de soro na obtenção de leites fermentados contendo probióticos". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/9/9133/tde-11112016-112019/.
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Os produtos lácteos probióticos e/ou simbióticos são líderes dentro do mercado de alimentos funcionais e prioridade de pesquisa em diversos países. A presença de bactérias probióticas viáveis e em alto número no produto durante sua vida de prateleira é condição essencial para assegurar o efeito probiótico. As bactérias probióticas apresentam crescimento lento no leite. O uso de co-culturas e a suplementação do leite são técnicas para superar esta dificuldade. O presente trabalho teve como objetivo verificar as condições de crescimento de Lactobacillus rhamnosus e Lactobacillus acidophilus em cultura mista com Streptococcus thermophilus em leite suplementado com hidrolisado de caseína e proteína concentrada de soro em diversas proporções (3,05 a 17,05g/L). Os parâmetros cinéticos velocidade de acidificação, tempo para atingir a velocidade máxima, tempo para atingir pH 5,0 e tempo para atingir pH 4,5 foram analisados, assim como as características físico-quimicas dos leites fermentados e a viabilidade das bactérias probióticas. A metodologia de superfície de resposta foi empregada visando otimizar a suplementação. O desempenho dos probióticos foi comparado com o leite fermentado pelas bactérias normais do iogurte nas mesmas condições. Ambos suplementos afetaram a acidificação do leite, sendo possível reduzir o tempo de fermentação. Em todos os ensaios, o nível de probióticos obtido esteve acima de 106 UFC/mL, valor mínimo de microorganismos viáveis sugerido por diversos autores para obter o efeito benéfico. Foi possível identificar modelos matemáticos preditivos.Dairy products containing probiotics and/or symbiotics are leader in the functional foods market and, priority in research worldwide. The use of casein hydrolysate and co-cultures are useful to lower fermentation time, and, in addition, it enhances the probiotic stability. The aim of the work was to verify the growing conditions of Lactobacillus rhamnosus and Lactobacillus acidophilus in mixed cultures with Streptococcus thermophiles in milk supplemented with casein hydrolysate and whey protein with different amounts (3,05 to 17,05g/L). Response surface methodology was used to establish adequate relationship of casein hydrolysate and whey protein contents aiming their optimization. The performance of probiotic bacteria was compared with those of yogurt bacteria. The supplements influenced milk acidification. In all experiments, probiotic levels were higher than 106 cfu/mL, the minimal viable number suggested by many authors to have therapeutic benefits. Mathematical models were developed.
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Minabe, Masaharu. "The lipids of post-fermentation yeast". Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/1487.
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Plunkett, Andrew David. "The influence of fermentation on extruded food products". Thesis, Manchester Metropolitan University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252433.
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The use of artificial flavourings and colours is common in the production of extruded snack food products. The problem with this process is two-fold, firstly the flavour is only present on the exterior of the product and secondly there is the risk of contaminating the product. The latter of these two problems is heightened by the fact that there is usually no further preservation treatment (heat, pressure, radiation) after flavouring. The aim of this study was to investigate the use of fermentation as a means of introducing both colour and flavour in extruded products. Model systems based upon a simplified traditional sourdough rye bread, was developed in order to study the influence of fermentation on the physical and chemical properties of extruded products. Using both the dry and liquid feeds, various fermented mixtures were extruded under a standard set of process conditions (feed rate 20 Kg/Hr, screw speed 200 rpm, feed moisture content 17% and die aperture 4mm). The fermentation process, although started with bakers yeast was greatly influenced by the establishment of a population of lactic acid bacteria from the natural microflora of the cereal flours. The total titratable acidity (measured as lactic acid) and pH of the slurries extruded via the liquid feed system were found to be in the ranges 0.73-1.28 % (dry basis) and 4.84-5.39 respectively. Levels of acidity and pH in samples extruded via the dry feed were determined to be in the ranges 0.77-1.67 % and 4.92-5.41 respectively. Increases in the fermentation time and hence levels of acidity, produced changes in the colour of the extrudates. Changesin the pressuret,o rque,s crews peed,a nd productt emperatured uring extrusionw ere also affected by changes in the fermentation process. This in turn was reflected in the physicalp roperties( expansiond, ensitya ndb reak strength)o f the extrudate. Analysis of the compounds found in the headspace of the fermented samples, using gas chromatography/mass spectrometry (GCMS), identified 97 compounds including alcohols, esters and carbonyl compounds. Concentrations of these compounds varied between 3 and 5012 ppb, with a number of compounds found to be present at levels well above their reported aroma thresholds. Retention of the identified compounds in the extrudate was found ix to be low however, samples produced from lower moisture dough systems showed retention of a number of compounds at levels known to be detectable by the human senses. Factors influencing the retention of the aroma compounds appear complex and could not be directly attributed to changes in the fermentation processes. Future studies of the effects of fermentation on the starch and protein fractions at a molecular level were suggested. It was concluded that, fermentation could present opportunities for the development of novel expanded snack products that avoid the pitfalls of current flavouring processes. X
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Delclos, Paul-R. Mrocek. "Vegetable preservation by a mixed organic acid fermentation". Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/842740/.
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Lactic acid fermented fruit and vegetables are normally obtained following a natural spontaneous fermentation in which no starter cultures are added. It could be expected that a suitable starter culture would help standardise production. Several lactic acid bacteria were selected for a series of physiological studies, in a defined medium (MRS broth) and in carrot juices, under varying conditions of growth temperature, salt concentration and carbohydrate source. Based on these, the homofermenter Lactobacillus pentosus and the heterofermenter Leuconostoc mesenteroides were tested as potential starters, in single and mixed cultures, for the fermentation of carrots (Daucus carota), as a novel fermentable substrate, and cabbage (Brassica oleracea) into sauerkraut. Fermentations were performed in the presence of the natural microflora. Sugar catabolism and acid production were monitored through H.P.L.C. In the fermentation of carrots Leuconostoc mesenteroides played a major role, with no homofermenters present. For sauerkraut, the mixed starter culture composed of Leuconostoc mesenteroides and Lactobacillus pentosus gave the closest resemblance to the product normally obtained following a natural commercial fermentation. The inclusion of the heterofermenter provided the required acid balance for correct product flavour and aroma by enhancing production of acetic acid. Acetate is also a better antimicrobial than lactate. A shorter fermentation time was also obtained, reducing the time from 3-4 weeks in the natural fermentation to only 7 days with the use of the mixed starter. When reduced salt concentrations were tried, 1% NaCl (w/w) resembled the spontaneous fermentation more closely, in regard to microbial sequence, pH and total acidity. Different ratios of the two lactic acid bacteria in combination were tried, the best being that in which L, mesenteroides and L. pentosus were initially present in the same proportions. Survival of Listeria monocytogenes in fermenting sauerkraut was shorter when starter cultures were used, but no difference was detectable between mixed and single cultures.
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Mendoza, L. S. "The microbiology of cooked rice and fish fermentation". Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356490.
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Economides, Aristodemos G. "Chemical changes induced by fermentation with saccharomyces species". Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292728.
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Fairbrother, Paul. "The fermentation of cheese whey by Lactobacillus helveticus". Thesis, University of South Wales, 1991. https://pure.southwales.ac.uk/en/studentthesis/the-fermentation-of-cheese-whey-by-lactobacilius-helvecticus(32b72e44-3d2a-4fcb-85d4-9b34263bd05e).html.
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The lactic acid fermentation of cheese whey permeate by Lactobacillus helveticus was studied. Precipitate formation during autoclaving of whey permeate was examined. Precipitation was found to be pH and temperature dependent. Qualitative analysis suggested that the precipitate was a calcium-phosphate complex. Solubilisation was achieved both by acidification and use of the sequestering agent EDTA. Optimisation of L. helveticus growth in whey permeate was carried out using factorial design, as opposed to a traditional univariate approach. Using this technique, the variation of specific growth rate with pH, temperature and stiirer speed was assessed. Cell growth and lactic acid formation in whey permeate containing various supplements, were investigated. Yeast extract was the most effective nitrogen/growth factor supplement. Maximum lactic acid production was achieved in permeate containing yeast extract (0.75% w/v), Tween 80 (0.1% v/v) and sodium acetate (0.05% w/v). Optimisation of lactic acid production in supplemented whey permeate was performed using factorial design. Optimum conditions for both acid formation and cell growth were pH 5.9, temperature 42°C and stirrer speed 200 rpm. Fourier transform infrared spectroscopy was applied to the on line and off line quantitative analysis of lactose and lactic acid during the fermentation process. This technique enabled substrate and product levels to be assessed quickly and simply, with no sample pre-treatment. Continuous culture of L. helveticus in MRS medium and supplemented whey permeate was carried out. Substrate conversion and lactic acid productivity decreased with increasing dilution rate. Maximum productivity corresponded to a dilution rate of 0.3 h" 1, whereas minimum residual substrate occured at a dilution rate of 0.1 h' 1 . Translation of the fermentation process from bench scale (11) to pilot scale (161) appeared to be successful. Completion times, productivity and lactose utilisation compared favourably with bench scale results.
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Krikorian, Eric Robert. "Anaerobic Fermentation of Food Waste and Glycerol to Hydrogen". DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1781.
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ABSTRACT
Anaerobic Fermentation of Food Waste and Glycerol to Hydrogen
Eric Krikorian
Hydrogen has several well-known advantages as a fuel and chemical feedstock, but current methods of hydrogen production are costly and energy intensive. A potentially advantageous source of hydrogen is fermentation of organic wastes, especially any abundant, low-cost wastes with a high content of simple sugars. Molar hydrogen yields from fermenters (aka digesters) are affected by pH, organic loading rate (OLR), hydraulic residence time (HRT), and substrate type. A less studied process to increase yield is sparging with low-H2 content gas to strip H2 from the digester liquid. The present study optimized the levels of each of these variables for hydrogen production from glycerol and food waste, building on previous proof-of-concept studies that used glucose as the substrate.
Six bench-scale, semi-continuously fed, stirred, anaerobic digesters were constructed and fed glycerol or food waste as a substrate. In a series of experiments, pH, HRT, OLR, and gas sparging rate were tested over a range of values. pH levels were controlled by use of phosphate buffers. In an envisioned process, low-H2 content from a second-stage methane digester would be used as the sparging gas, allowing subsequent combustion of a high-H2 content biogas with low NOx formation potential. N2 was used as a surrogate for biogas in one set of experiments.
The main conclusions are based on data from periods of steady-state digester performance and daily measurements of pH, alkalinity, biogas production, biogas composition, total and volatile suspended solids, and chemical oxygen demand (COD). COD balances were measured for all experiments and generally showed recoveries of >85%.
With glycerol substrate, the highest molar hydrogen yield (0.071 ± 0.0100 mol H2/mol glycerol) and volumetric hydrogen production (0.281 ± 0.0395 LH2/LReactor-day) were achieved with the following: pH 6.51, OLR 18.8 g COD/L-day, HRT 12 hours, and sparging rate of 3.2 mL/min, and 1-L working volume. Gas type (N2 or biogas) used in sparging did not influence hydrogen production.
The best results with food waste (0.021 ± 0.0013 mol H2/mol COD and 0.478 ± 0.0280 L H2/LReactor-day) were obtained with the following conditions: OLR 33.9 g COD/L-day and nitrogen sparging rate of 1.0 L N2/hour, and 1-L working volume. pH and HRT were not optimized for food waste substrate, but the best values from the glycerol experiments were adopted.
Sparged glycerol and food waste digesters had molar hydrogen yields at least 40% greater than controls. Nonetheless, molar hydrogen yields in the present study were lower than in those reported by other authors, for unknown reasons. Yields from food waste might be improved by optimizing pH and HRT levels. Alkalinity sources need to be identified to replace the non-scalable phosphate buffers of the present research. Lastly, long-term experiments should consider whether attached growth of hydrogen-consuming methanogens develops in hydrogen fermentation reactors.
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Sparringa, Roy Alexander. "Growth and protein utilisation by Rhizopus oligosporus during tempe fermentation". Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298415.
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Veiga, da Cunha Maria de Almada Cardoso. "Co-fermentations of sugar and glycerol by lactobacilli". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280007.
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Graffham, A. J. "Tempe fermentation as a processing option for African cowpea". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240292.
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Drysdale, Conor R. "Organic acid production by the microbial fermentation of sucrose and inulin". Thesis, Queen's University Belfast, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266703.
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Mugocha, Petronella Tapiwa. "Fermentation of a finger millet-dairy composite gruel". Thesis, University of Pretoria, 2001. http://hdl.handle.net/2263/30547.
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Mashayekh, Morteza. "Evaluation of Frogurt: A New Product Prepared by Fermentation of Ice Cream Mix". DigitalCommons@USU, 1988. https://digitalcommons.usu.edu/etd/5349.
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Ice cream mix was fermented with yogurt cultures of Streptococcus thermophilus and Lactobacillus bulgaricus to four different pH's then frozen in a batch ice cream freezer. A consumer panel of 120 people tasted samples of strawberry flavored product with pH's of 4.4, 4.7, 5.1, and 5.4 and commercial frozen yogurt as a standard. Results from the panel were used to predict a preferred pH of 4.9. Another panel of 181 people compared product at pH 4.9 with 10, 15 and 20% strawberry flavoring. There was not a statistically significant difference among levels of flavoring.
Starter culture populations and lactase activity were monitored for one month both in yogurt and in the frozen fermented ice cream mix. Lactase activity and colony counts progressively decreased in refrigerated yogurt at 4°C during the 30-day period. In frozen fermented ice cream mix, lactase activity and colony counts decreased slightly. The fermented ice cream mix can be held frozen for more than one month with active lactase activity, and viable colony counts, but refrigerated yogurt does not have a shelf life of more than one month.
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Chaveesuk, Ravipim. "Accleration of fish sauce fermentation using proteolytic enzymes". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60539.
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First grade and second grade Nampla, commercially produced Thai fish sauces, were analyzed for their chemical and microbiological composition. First grade commercially produced Nampla contained higher amounts of total nitrogen, formol nitrogen, free and total amino acids compared to second grade sauce. Most of the essential amino acids were present in both grades of sauces. Low microbial counts of halotolerant microorganisms were observed in both sauces. The use of trypsin and chymotrypsin to accelerate the rate of fish sauce fermentation produced from herring, one of the underutilized fish species in Quebec, was investigated. Results showed that supplementation with trypsin and chymotrypsin increased significantly the rate of proteolysis, the amounts of total nitrogen, formol nitrogen and free amino acids in the final fish sauces (p 0.05). (Abstract shortened by UMI).
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Zhao, Renyong. "Impact of sorghum proteins on ethanol fermentation and investigation of novel methods to evaluate fermentation quality". Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/1036.
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Richelle, Anne. "Modelling, optimization and control of yeast fermentation processes in food industry". Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209280.
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A macroscopic model describing the main physiological phenomena observed during the fed-batch baker’s yeast production process and including the influence of nitrogen on the key bio-mechanisms is proposed. First, on the basis of a set of biological reactions, inspired by the model of Sonnleitner and Käppeli, a model in which the nitrogen and glucose consumption are coordinated is proposed. Second, an attempt of estimating storage carbohydrate contents in yeast cells through an extension of this model is presented. The model is identified and validated with experimental data of fed-batch yeast cultures and successfully predicts the dynamics of cell growth, substrate consumption (nitrogen and carbon sources) and metabolite production (ethanol and storage carbohydrates). The developed model was used for the determination of optimal operating conditions, in the sense of a production criterion. To this end, two different approaches were used: a control vector parameterization approach and a semi-analytical formulation of the optimal operating policy. The two approaches were compared with numerical and experimental data. The results of the two approaches lead to the determination of similar optimal operation conditions, which have been implemented for a new experimental phase. Moreover, these optimal conditions are in agreement with the profiles obtained by industrial manufacturers through an empirical optimization of the process.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Yousuf, Zarina. "Development and potential of two novel reporter systems for use in lactic acid bacteria". Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326434.
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Layfield, Johnathon Blake. "Characterization of Hybrid Strains of Saccharomyces pastorianus for Desiccation Tolerance and Fermentation Performance". NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-08182009-130032/.
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Dry yeast can be utilized in both ale and lager beer production to provide an inexpensive source of large amounts of viable cells for fermentation. This study examines the desiccation tolerance of different strains of S. pastorianus and the subsequent fermentation performance in comparison to S. cerevisiae. The use of active dry brewerâs yeast (ADY), Saccharomyces cerevisiae, as a starter for the production of ales has been gaining popularity within the brewing industry, spurring manufactures to also produce active dry lager yeast (ADLY), S. pastorianus. The drying process is known to have a greater negative effect on the cell viability and physiology of ADLY than that of ADY, possibly due to the fastidious growth, low production temperature and poor thermotolerance of S. pastorianus. This may result in lower cell viability and concentration of ADLY starter cultures, which could lead to stuck or slow fermentations. S. pastorianus is a hybrid organism resulting from a cross between S. cerevisiae and S. bayanus. It has been proposed that it can be categorized into two distinct groups: Group 1 (S. pastorianus- Saaz type) has lost a significant amount of the genomic content contained within S. cerevisiae and is therefore closer to S. bayanus; while Group 2 (S. pastorianus- Frohberg type) has retained almost all of the genomic content of S. cerevisiae. To investigate whether these two groups differ in their tolerance to desiccation, both groups of S. pastorianus were spray dried at 140oC and rehydrated in phosphate buffer at 25oC for 30 minutes. The viability of the rehydrated cultures was determined using microscopic and viable cell counts. The fermentation performance of the cultures was tested by inoculating equal counts of viable rehydrated cells into brewerâs wort and monitoring changes in cell count, carbohydrate and alcohol concentration until completion. The findings suggest that the S. pastorianus- Frohberg type is less tolerant to desiccation than either S. cerevisiae or S. pastorianus- Saaz type. The Frohberg type shows evidence of membrane damage which could delay the onset of fermentation. Utilization of the correct strain of ADLY could reduce the possibility of contamination or extended lag phases leading to stuck fermentations.
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Hagelin, Johnny. "Enhancement of hydrolysis from co-fermentation of food waste and primary sludge". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299643.
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Research about resource recovery from complex waste streams is getting an increased scientific attention since valuable resources can be produced by sustainable biological means. In anaerobic degradation processes, resources such as volatile fatty acids (VFAs) and biogas are highly coveted. One of the key parameters affecting the yield of resources is the hydrolytic efficiency in the waste stream by hydrolytic bacteria. The aim of this study was to examine how bioaugmentation can be implemented as a strategy to enhance hydrolysis in complex waste streams. In pursuit of this aim, three selected species of hydrolytic bacteria, Bacteroides thetaiotaomicron, Bacteroides amylophilus and Bacteroides ruminicola were inoculated both in pure culture combinations and bioaugmented with granular sludge as mixed culture in reactors. The studied waste stream was food waste mixed with primary sludge collected from Henriksdals wastewater treatment plant at Stockholm, Sweden. The highest hydrolytic efficiency (90%) was reached by the pure culture fermented reactor inoculated with Bacteroides thetaiotaomicron and Bacteroides ruminicola. This efficiency was measured at day 10 after reactor set-up. Among the bioaugmented reactors, highest hydrolytic activity (66%) was achieved by the reactor inoculated with Bacteroides thetaiotaomicron and it was measured at day 10. The increase in hydrolytic efficiency for bioaugmented reactors was slower compared to pure culture fermented reactors and the most probable reason to that is due to competition amongst introduced species and pre-existing mixed culture in granular seed sludge.Mer uppmärksamhet riktas till forskning kring resursåtervinning från komplexa avfallsströmmar eftersom värdefulla resurser kan produceras genom mer hållbara biologiska tillvägagångssätt. I anaeroba nedbrytningsprocesser är produkter såsom flyktiga fettsyror (VFAs) och biogas mycket eftertraktade. En av huvudparametrarna som påverkar utbytet av återvunna resurser är den hydrolytiska effektiviteten i avfallsströmmen av hydrolytiska bakterier. Syftet med studien var att undersöka hur bioaugmentering kan implementeras som strategi för att förstärka hydrolys i komplexa avfallsströmmar. Därav utfördes fermentering med tre valda hydrolytiska bakterier, Bacteroides thetaiotaomicron, Bacteroides amylophilus och Bacteroides ruminicola både i renkultur och bioaugmenterat med granulärt slam som mixad kultur i reaktorer. Avfallsströmmen som studerades var matavfall mixat med primärt slam hämtat från Henriksdals vattenreningsverk i Stockholm, Sverige. Högsta hydrolytiska effektivitet (90%) uppnåddes för reaktorn inokulerat med Bacteroides thetaiotaomicron och Bacteroides ruminicola i renkultur. Denna effektivitet uppmättes dag 10 efter reaktorerna sattes upp. För de bioaugmenterade reaktorerna så uppnåddes högsta hydrolytiska effektivitet (66%) dag 10 av reaktorn inokulerat med Bacteroides thetaiotaomicron. Ökningen i hydrolytisk effektivitet var långsammare för de bioaugmenterade reaktorerna jämfört med reaktorerna med renkultur. Den mest sannolika förklaringen till det är tävling om näringsämnen och vitaminer mellan introducerade bakterier och de bakterier som redan existerar i det granulära slammet.
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Olsen, Maegan Jessie. "Redox Potential Trends of Cucumber Fermentation as Influenced by Microbial Growth and Gas Purging". NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-11052008-141935/.
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Determining the redox potential of a system can be a useful tool in evaluating the thermodynamic changes that occur over a period of time. Currently, fermentation industries use pH measurements to assess the progress of fermentation and growth of lactic acid bacteria (LAB). Redox potential (Eh) measures the transfer of electrons within a system, rather than solely the concentration of hydrogen ions, as measured by pH. Continuous monitoring of fermentation by Eh may allow for more descriptive analysis of the metabolic process and could offer a method for the earlier prediction of spoilage by yeasts. The trends in redox potential of fermenting cucumbers were observed to evaluate the possible application of this parameter in monitoring the development of fermentation. Additionally, an evaluation of the effect of gas purging on microbial growth during the fermentation was conducted using redox potential trends as a monitoring tool. Cucumbers were packed and brined using sodium chloride, calcium chloride, and acetic acid and the redox potential monitored during fermentation. Examination of both pasteurized-inoculated jars and non-pasteurized jars was conducted in this study. In addition, changes in redox potential were measured in fermentations that were purged with nitrogen, oxygen, hydrogen, or left untreated. Brine samples were analyzed for microbial counts, pH and substrates and products of fermentation. Under conditions representative of a standard cucumber fermentation, a dramatic decrease in the redox potential was observed during the first day, concomitantly with the initiation of the log phase of bacterial growth. However, in the presence of spoilage yeast, redox potential remained low over this initial period. The progress of a fermentation sparged with nitrogen, oxygen, or no treatment produced similar Eh trends. The Eh trend was more reduced under hydrogen sparging. A heightened growth rate for LAB, more efficient production of lactic acid, and lower production of ethanol occurred with nitrogen sparging. The evidence suggests that the growth of yeasts in a cucumber fermentation could be detected based upon differences in the redox potential. Distinct variations in Eh were still recorded after pH values decreased and remained constant, suggesting the valuable possible application of Eh to monitor industrial cucumber fermentations. Additionally, changes in redox potential were affected by gases introduced during cucumber fermentations and sparging with nitrogen could have substantial benefits to the industry.
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Al-Jedah, Jasim Hasan. "Mehiawah - a fish sauce from the Gulf region". Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284434.
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Dawson, Lynne Evelyn Rosemary. "Examination of factors influencing the voluntary food intake of grass silage by ruminants". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295409.
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Bui, The Truong, University of Western Sydney, of Science Technology and Environment College y Centre for Advanced Food Research. "A study of Vietnamese soy sauce fermentation". THESIS_CSTE_CAFR_Bui_T.xml, 2003. http://handle.uws.edu.au:8081/1959.7/635.
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Vietnamese soy sauce has been made for centuries using traditional methods, in villages in Northern Vietnam. This sauce differs from other Asian products not only in its raw materials but also in its flavour characteristics. Presently small scale Vietnamese soy sauce is produced mostly with a standardised inoculum of Aspergillus oryzae under natural conditions. This usually gives rise to a product of variable and inconsistent quality. The aim of this study was to standardise the fermentation condition for the production of Vietnamese soy sauce, so as to obtain a product of more consistently good quality. Aspergillus flavus var columnaris was used as the inoculum. The inoculum was prepared by growing the organism on sticky rice at 20 and 37 degrees centigrade under aerobic conditions. At 20C, a high protease activity was recorded in the inoculum while at 37C, a high amylase activity was observed. The two different inocula prepared at 20C and 37C were then used in the preparation of soy sauce in the normal manner. The inocula were mixed with cooked roasted soy beans and salt water, left to age for 1 month at 30C, followed by ageing at 20C for 2 months. The products obtained were subjected to sensory evaluation and analysed for glucose, fructose, amino acids, nitrogen, ethanol and NaCI. Both inocula produced products of acceptable quality. The inoculum produced at 20C had a higher sensory evaluation score. It also contained a higher level of protein (14.5% compared to 11%), and a higher sensory evaluation score (6.9 compared to 3.2) when compared to a commercial Vietnamese sauce, Hanoi soy sauce. This valuable information will now enable small scale producers to produce this product throughout the year by controlling the temperature, and not be limited to the summer season, as has been the case with the traditional method of production.Master of Science (Hons)
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Koren, David W. "Production of fructose and ethanol by selective fermentation of glucose-fructose mixtures". Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7944.
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In this project the selective conversion of glucose to ethanol from glucose/fructose mixtures was investigated. The process was carried out using a mutant of Saccharomyces cerevisiae, batchwise, continuously with immobilized cells and semicontinuously. The kinetic behaviour of S. cerevisiae ATCC 36859 was studied using batch fermentation data. The growth of the yeast is inhibited equally by glucose and fructose, even though fructose is not consumed by the yeast. Fermentation models were formulated in this work. These models include terms which account for the inhibition of growth, glucose consumption and ethanol production by the carbohydrate and ethanol. The models predict that the growth rate of the yeast will be zero if the medium contains either 488 g/L total carbohydrates of 62 g/L ethanol. Batch tests were carried out with hydrolyzed Jerusalem artichoke juice and High Fructose Corn Syrup. An ethanol productivity of 21 g/Lh was attained in a batch process using an initial biomass concentration of 94 g/L. It was found though that this process suffered from the inhibitory effects of high total carbohydrate concentrations, therefore products containing high fructose concentrations were produced with lower ethanol productivities. In addition, reuse of the biomass resulted in a reduction of 40% in its activity. The cells were immobilized in calcium alginate beads and placed in a tubular reactor. In this form they were used for more than 1000 hours without a loss of activity. A syrup containing fructose as 99% of the reducing sugars was produced from synthetic as well as from food grade glucose/fructose mixtures. A maximum ethanol productivity of 13 g/Lh was attained. A product containing 76 g/L ethanol was also produced in this process. The productivity of the reactor was reduced as the total carbohydrate concentration was increased, therefore products with a high fructose concentration ($>$150 g/L) could not be formed without a significant drop in the productivity using the immobilized cells. The inhibitory effects of high total carbohydrate concentrations were reduced by using a fed batch process. In this scheme, 42 High Fructose Corn Syrup was used with and without added nutrients as the feed solution; sterilization of the syrup was not necessary due to its high solids concentration. The syrup was continuously fed to a bioreactor, the glucose was converted to ethanol while the fructose accumulated. A syrup containing 257 g/L fructose and 68 g/L ethanol was produced in this process. The product formed in the process was purified with activated carbon and ion-exchange resin. A clear and colourless fructose syrup that visibly resembled HFCS was produced. The ethanol in the product allowed for storage of the product for long periods of time before its further treatment. (Abstract shortened by UMI.)
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Coleman, Jr Stanley Albert. "Continuous fermentation of food scraps with constant pH control to produce carboxylic acids". Texas A&M University, 2007. http://hdl.handle.net/1969.1/85797.
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Global energy demands combined with environmental restrictions are fueling a
move to alternative energy sources. Biofuels are formed from biomass; the MixAlco
process is one such method. In this work, food scraps are explored as a potential
feedstock to the MixAlco process. Batch fermentation with various temperatures,
buffers, and pH control methods elucidated the behavior of food scraps during
fermentation. The pH and reactor configuration were limiting factors when maximizing
production. A fermentor was developed and tested with constant pH control. This
resulted in elevated concentration (100 g/L) and selectivity (82%) of desired products.
The fermentation resulted in elevated concentrations, but low conversion of
solids. The undigested material may serve as a nutrient source for fermenting
lignocellulosic feedstocks. Combining various nutrient sources with lignocellulose, such
as bagasse, resulted in additional production and further conversion. Multiple nutrient
sources were tested resulting in total acid concentration ranging from 20.2 to 34.5 g/L.
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Elzwai, Jamal Ibrahim Mohamed. "Occurrence and conditions of production of Ochratoxin A in food fermentation in Libya". Thesis, Glasgow Caledonian University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443238.
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Gurban, Ana-Maria. "Biosensors based on dehydrogenases for food and environmental monitoring". Perpignan, 2006. http://www.theses.fr/2006PERP0922.
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Les déshydrogénases NAD-dépendantes constituent une classe d’enzymes particulièrement attractives pour le dosage de nombreux substrats dans le domaine agro-alimentaire, et en particulier dans le secteur viti-vinicole. Cette thèse de doctorat décrit la mise au point de biocapteurs ampérométriques pour le contrôle de la fermentation malolactique du vin. Les différents capteurs développés sont basés sur des systèmes bi-enzymatiques couplant la malate déshydrogénase (MDH) à une NADH oxydase, ou sur des systèmes mono-enzymatiques associant la MDH ou une malate-quinone oxydoréductase (MQO) à des médiateurs électroniques judicieusement sélectionnés. Des capteurs utilisant une aldéhyde déshydrogénase ont été également décrits pour la détection de fongicides et fumigants de la famille chimique des dithiocarbamatesNAD-dependent dehydrogenases constitute a particularly attractive class of enzymes for the determination of various substrates in agrifood industry, and more specifically for wine industry. This thesis describes the development of amperometric biosensors for the monitoring of malo-lactic fermentation of wine. The different sensors designed are based either on bi-enzymatic systems coupling malate dehydrogenase (MDH) and NADH oxidase, or on mono-enzymatic systems associating MDH or a malate-quinone-oxidoreductase (MQO) with suitable electronic mediators. Sensors incorporating an aldehyde dehydrogenase are also described for the detection of dithiocarbamate fungicides and fumigants
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Yamada, Kathryn K. "INACTIVATION OF FOODBORNE PATHOGENS DURING CIDER FERMENTATION, IN A CIDER MODEL SYSTEM AND COMMERICAL CIDER". DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2134.
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Hard cider is an alcoholic drink made from fermented crushed fruit, typically apples. The popularity of this fermented alcoholic beverage has been on the rise within the last decade. Historically, hard cider has been deemed safe due to the presence of ethanol and the low pH. Although there is lack of scientific evidence to prove that hard cider will and can be safe from foodborne pathogens. Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes are three predominate foodborne bacterial pathogens of concern in the food and beverage industry. Escherichia coli O157:H7 in particular has been associated with fresh produce and more specifically apples, and apple products such as apple juice. The purpose of this study was to determine the bactericidal effects of pH, ethanol, and malic acid on Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes to evaluate the safety parameters for safe hard cider production and storage.
The fate of foodborne pathogens in cider was determined during hard cider fermentation, in a cider model system, and in commercial cider. Escherichia coli O157:H7, Salmonella spp, and Listeria monocytogenes did not survive a 5-day fermentation period resulting in a > 7 log CFU/mL reduction of each pathogen with no significant change in pH. The final ABV of the cider at the end of the 5-day fermentation was 4.4%. In the cider model system, the lower the pH and higher the ABV the quicker die off was observed, at pH 2.8, 3.0, 3.2, and 3.4 with 7, 8, and 9% ethanol concentration there was a 6.6 log reduction in E. coli O157:H7 population after 1 day. By the 7-day incubation period, no pathogens were detected at all pH and ABV combinations except for at pH 3.6 and 3.8 with 4% ethanol having ≤0.6 log CFU/mL of the population surviving. Similar E. coli O157:H7 inactivation patterns were observed in the model system and in the commercial ciders. The six commercial ciders observed had varying pH, ABV (%), and malic acid concentrations but successfully resulted in a > 6 log CFU/mL reduction in population of E. coli O157:H7 within 4 days of incubation. The ciders with the highest ABV’s, 8.7 and 9.6% observed a > 6 log reduction by 1 day. It was observed that at some point in time pH plays a bigger role in the presence of less ethanol, but it is clear that ethanol and pH work synergistically to kill of pathogens present in cider fermentation, a cider model, and commercial cider.
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Rycroft, Catherine Elaine. "A comparative in vitro evaluation of the fermentation properties of potential prebiotic food ingredients : investigating structure-function relationships". Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391347.
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Ali, Rowayda [Verfasser] y H. [Akademischer Betreuer] Horn. "Propionic acid production through anaerobic fermentation of food waste / Rowayda Ali ; Betreuer: H. Horn". Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1225401186/34.
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Dornan, Susan. "Aspects of genetic instability in Lactococcus lactis". Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334525.
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Poe, Nicholas Edward. "Acetone, Butanol, and Ethanol (ABE) Production from Food Waste via Clostridium beijerinckii". Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/96601.
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Annually, approximately 150 million metric tonnes of food goes to waste in the U.S., potentially causing economic loss and environmental pollution. Fermentation of food waste to produce acetone, butanol and ethanol (ABE) via fermentation has the potential to valorize food waste by producing value-added chemicals. However, the composition of food wastes from different sources vary, which affects ABE fermentation performance and hinders the commercialization of food waste fermentation. The objective of this study is to investigate the compositional variation of food waste collected weekly for 16 weeks (a total of sixteen samples) and determine how this variation affects ABE fermentation performance. Samples collected from Southgate Center, a food processing facility operated by Virginia Tech Dining Services, was characterized for use as a feedstock for ABE fermentation. Water, sugar, starch, fiber, protein, fat and ash concentrations in each of food waste samples were determined. ABE fermentation of these wastes was performed using Clostridium beijerinckii via batch fermentations. Correlations of ABE and butanol yields with the individual components of food waste composition were performed to better understand which components are key to ABE fermentation.
Overall, this study demonstrated the feasibility of using food waste as a viable feedstock for ABE fermentation and investigated the effect of variation of food waste composition on the ABE fermentation performance. In the 16 collected samples, each major compositional attribute exhibited high variability. The concentration of total soluble sugar, defined as glucose, fructose, sucrose for the purposes of this experiment, ranged from 0.5 to 53.5% (dry basis) among different food waste samples. The concentration ranges of total starch, neutral detergent fiber (NDF), crude protein, crude fat and ash were 0 to 23.4% (dry basis), 0.6 to 25.8%, 5.5 to 21.2%, 0.1 to 37.9%, 1.4 to 13.7%, respectively. The high variation of food waste composition resulted in a high variation of ABE yield when these food wastes were subjected to fermentation by C. beijerinckii. The total ABE concentration following fermentation ranged between 6.9 to 17.0 g/L with an average value of 13.2 g/L. ABE and butanol concentrations are positively correlated with starch and equivalent glucose, i.e., the sum of initial free glucose and glucose that could be theoretically hydrolyzed from starch and sucrose during fermentation, but is negatively correlated with NDF concentrations.Master of Science in Life Sciences
Nearly 40% of food in the U.S. goes to waste, causing a huge amount of economic loss and environmental pollution. Use of microorganisms to ferment food waste is a viable way to mitigate many of the issues associated with food waste. Put simply, fermentation is a biological process in which an organic substrate, such as food waste, is consumed and a more valuable product is produced. In this study, different food wastes were collected from the campus food processing center weekly for 16 weeks. Water, sugars, starch, fiber, protein, fat and ash contents of the collected food wastes were determined. Fermentation of these food wastes were conducted using a microorganism called Clostridium beijerinckii. The results showed that there was a high variation amongst the composition of the food waste samples. The concentration of total soluble sugar (glucose, fructose, sucrose) ranged from 0.5 to 53.5% (dry basis) among different food waste samples. The concentration ranges of total starch, neutral detergent fiber (NDF), crude protein, crude fat and ash were 0 to 23.4% (dry basis), 0.6 to 25.8%, 5.5 to 21.2%, 0.1 to 37.9%, 1.4 to 13.7%, respectively. The variation of food waste composition also led to different fermentation yields. It was also found that a higher glucose content in food waste results in a higher fermentation product yield; however, a higher fiber content in food waste results in a lower fermentation product yield.
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Theron, Karin Alicia. "Sensory and phenolic profiling of Cyclopia species (Honeybush) and optimisation of the fermentation conditions". Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/19945.
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Thesis (MSc Food Sc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The sensory profiles, phenolic composition and colour of honeybush infusions, prepared from six Cyclopia species (C. sessiliflora, C. longifolia, C. genistoides, C. intermedia, C. subternata and C. maculata), were determined to establish the variation between species. The results of the sensory study were used to create a honeybush sensory wheel and lexicon. The “characteristic” sensory profile of honeybush tea can be described as a combination of floral, sweet, fruity and plantlike flavours with a sweet taste and a slightly astringent mouthfeel. Sensory results indicated that the species could be divided into three distinct groups; group A (C. sessiliflora, C. intermedia and C. genistoides), group B (C. longifolia and C. subternata) and group C (C. maculata). Group A was associated with fynbos floral, fynbos sweet and plantlike attributes, group B with rose geranium and fruity sweet attributes and group C with woody, boiled syrup and cassia/cinnamon attributes. Gas chromatography-olfactometry analysis of the C. maculata aroma fraction indicated that the spicy note of its aroma could possibly be explained by the high concentration of the volatile component eugenol. However, none of the aroma impact volatiles had a specific cassia/cinnamon note. Large variation in the composition of the honeybush infusions was revealed through the quantification of the soluble solids, total polyphenol and individual monomeric polyphenolic compounds, as well as the absorbance (“colour”). Infusions of C. genistoides, C. longifolia and C. sessiliflora had the highest soluble solids and total polyphenol content, as well as the highest absorbance values. Only mangiferin, isomangiferin, hesperidin and compound C (unidentified compound) were detected in all six Cyclopia species. Cyclopia genistoides, C. longifolia and C. sessiliflora, in order of prominence, contained the highest concentration of both mangiferin and isomangiferin whereas C. genistoides and C. maculata contained the highest hesperidin content. The bitter taste present in certain Cyclopia species appeared to be due to a high mangiferin content, however, compounds such as isomangiferin and compound C might also have played a role. The effect of fermentation (oxidation) temperature (80°C and 90°C) and time (8 h, 16 h, 24 h and 32 h) of C. genistoides, C. subternata and C. maculata on the sensory characteristics of their infusions was also investigated. Fermentation for longer than 8 h resulted in an increase in positive sensory attributes and a decrease in negative sensory attributes rather than the formation of new sensory attributes. A fermentation temperature/time combination of 80°C/24 hours or 90°C/16 h was required for C. genistoides, C. subternata and C. maculata. Fermenting C. genistoides at 90°C would result in a honeybush infusion with slightly less rose geranium notes whereas C. subternata can be fermented at either 80°C or 90°C, depending on whether floral or apricot jam notes are desired. Cyclopia maculata should preferably not be fermented at 90°C due to an increase in negative sensory attributes (hay/dried grass and green grass). Fermentation reduced the soluble solids content, total polyphenol content, colour and concentration of individual polyphenolic compounds. Changes in the taste and mouthfeel of honeybush tea could be attributed to changes in the polyphenolic composition caused by the high temperature oxidation. Mangiferin associated with the bitter taste of C. genistoides, while in C. subternata astringency may be partly attributed to the mangiferin and isomangiferin content. The study substantiated the need for further research on the contribution of the major phenolic compounds towards the taste and mouthfeel of Cyclopia species.
AFRIKAANSE OPSOMMING: Die sensoriese profiel, fenoliese samestelling en kleur van heuningbostee, berei van ses Cyclopia spesies (C. sessiliflora, C. longifolia, C. genistoides, C. intermedia, C. subternata en C. maculata), is bepaal ten einde die mate van variasie vas te stel. Die resultate van die sensoriese studie is gebruik om 'n sensoriese wiel en leksikon vir heuningbostee te ontwikkel. Die “karakteristieke” sensoriese profiel van heuningbostee kan beskryf word as 'n kombinasie van blomagtig, soet, vrugtig en plantagtige geure met 'n soet smaak en 'n effense frankheid. Sensoriese resultate het aangedui dat die spesies in drie groepe verdeel kon word; groep A (C. sessiliflora, C. intermedia and C. genistoides), groep B (C. longifolia and C. subternata) en groep C (C. maculata). Groep A is met fynbos blom, fynbos-soet en plantagtige geure geassosieer, groep B met roos geranium en vrugtige-soet geure en group C met houtagtige, gekookte stroop en kassia/kaneel geure. Gaschromatografie-olfaktometrie analises van C. maculata se aroma fraksie het getoon dat die speseryagtige aroma moontlik as gevolg van die hoë konsentrasie van die vlugtige komponent, eugenol, kon wees. Geen van die aroma-impak vlugtige verbindings het egter 'n spesifieke kassia/kaneelagtige noot gehad nie. Groot variasie in die samestelling van heuningbostee ten opsigte van die inhoud van oplosbare vastestowwe, totale polifenole en monomeriese fenoliese verbindings, asook die absorbansie (“kleur”) is aangetoon. Heuningbostee berei van C. genistoides, C. longifolia en C. sessiliflora het die hoogste oplosbare vastestowwe en totale polifenol inhoud, asook die hoogste absorbansie waardes gehad. Slegs mangiferien, isomangiferien, hesperidien en verbinding C (ongeïdentifiseerde verbinding) is in al ses Cyclopia spesies geïdentifiseer. Cyclopia genistoides, C. longifolia en C. sessiliflora, in volgorde van belangrikheid, het die hoogste konsentrasie van beide mangiferien en isomangiferin gehad teenoor C. genistoides en C. maculata wat die hoogste hesperidien konsentrasie gehad het. Die bitter smaak teenwoordig in sekere Cyclopia spesies blyk moontlik as gevolg van die hoë mangiferien inhoud te wees, hoewel komponente soos isomangiferien en komponent C dalk ook 'n rol mag speel. Die effek van die fermentasie temperatuur (80°C en 90°C) en tyd (8 h, 16 h, 24 h en 32 h) van C. genistoides, C. subternata en C. maculata op die sensoriese eienskappe van heuningbostee is ondersoek. Fermentasie vir langer as 8 h het tot 'n toename in positiewe sensoriese eienskappe en afname in negatiewe sensoriese eienskappe gelei eerder as die ontstaan van nuwe sensoriese eienskappe. Om heuningbostee met 'n optimum sensoriese profiel te verkry is 'n fermentasie temperatuur/tyd kombinaise van 80°C/24 h of 90°C/16 h nodig vir C. genistoides, C. subternata en C. maculata. Cyclopia genistoides wat by 90°C gefermenteer word sal minder van die roos geranium note bevat, terwyl C. subternata by 80°C of 90°C gefermenteer kan word, afhangende of 'n blomagtige of 'n appelkooskonfyt noot verlang word. Fermentasie by 90°C word nie aanbeveel C. maculata nie as gevolg van die toename van sekere negatiewe sensoriese eienskappe (hooi/droe gras aroma en -geur en groen gras aroma). Fermentasie het die inhoud van oplosbare vastestowwe, totale polifenole, individuele polifenoliese verbindings, asook kleur verminder. Veranderinge in die smaak en mondgevoel van heuningbostee kon toegeskryf word aan die veranderinge in die polifenoliese inhoud as gevolg van die hoë temperatuur oksidasie. Mangiferien is met die bitter smaak van C. genistoides geassosieer, terwyl mangiferien and isomangiferien moontlik deels frankheid in C. subternata veroorsaak. Die studie het die noodsaaklikheid vir verdere navorsing op die bydrae van die hoof fenoliese verbindings tot die smaak en mondgevoel van Cyclopia spesies gestaaf.
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Martins, Jose Francisco Pereira. "Raw meat fermentation : an approach to the study of selected characteristics of Pediococci and other lactic acid bacteria important to Brazilian salami processing". Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239476.
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Bedaso, Binyam. "Volatile fatty acid production from co-fermentation of primary sludge and food waste without pH control". Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263755.
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The production of volatile fatty acids (VFAs) from waste stream is gaining high attention because of their high market value and wide range of applications. In this study, the production of VFA from co-fermentation of primary sludge from wastewater treatment plant and food waste without pH control was evaluated using a pilot-scale reactor in a semi-continuous mode of operation. In addition, the influence of substrate and inoculum on VFA production and composition was assessed using a batch fermentation experiment. The pilot-scale reactor was operated at a retention time of 7 days and 10 days in phase 1 (126 days) and phase 2 (25 days) respectively. A maximum VFA production of (687 mg COD/g VS) was obtained when the pilot-scale reactor was operated at a retention time of 7 days on day 107. The change in retention time from 7 to 10 days led to a higher hydrolysis rate; however, no improvement in VFA production was observed. The most abundant VFA produced after the reactor stabilized was caproic acid (50 %), followed by acetic acid (23%) and butyric acid (20%). Higher amount ammonium nitrogen (1.3 to 14.32 mg/g VS) compared to soluble phosphorus (0.69 to 7 mg/g VS) was released during the co-fermentation process. Furthermore, the loss of the VFA due to the production of methane was highly reduced because the pH of the reactor adjusted by itself in the range of (5 – 5.7). The batch fermentation experiment revealed that VFA production without pH control is highly influenced by the type of substrate and inoculum used. While the distribution of VFAs, is highly influenced by the inoculum type compared to the substrate used. Finding from this study indicates that there is a potential to produce VFA from co-fermentation of primary sludge and food waste without pH control.Lättflyktiga fettsyror (VFA; eng. Volatile Fatty Acids) är viktiga byggstenar för produktionen av en mängd kommersiellt viktiga kemikalier. VFA produceras för närvarande från icke-förnybara petrokemiska källor, som kan orsaka miljöproblem på grund av utsläpp av växthusgaser. VFA kan också produceras som en mellanprodukt vid den anaeroba nedbrytningsprocessen. Produktionen av VFA från avfallsströmmar har i nuläget fått stort intresse på grund av dess höga marknadsvärde och breda applikationsområde jämfört med biogas. Det mesta av forskningen som hittills genomförts har dock baserats på justeringen av pH genom tillsatts av HCl eller NaOH. Denna metod har dock mindre storskalig praktisk användning på grund av hög konsumtion av kemikalier. I denna studie undersöktes produktionen av VFA från samjäsning av primärslam och matavfall utan pH-kontroll med hjälp av en pilotskalereaktor i ett semikontinuerligt driftläge. Dessutom mättes den påverkan substrat och inokulum hade på produktion och av VFA genom batchjäsningsexperiment. Pilotskalereaktorn drevs med uppehållstid på 7 dagar respektive 10 dagar i fas 1 (126 dagar) och fas 2 (25 dagar). Maximal VFA produktion (på 687 mg COD/g VS) uppnåddes på dag 107, när pilotreaktorn hade en uppehållstid på 7 dagar. Ändringen i uppehållstid från 7 till 10 dagar ledde till en högre hydrolystakt; dock observerades ingen förbättring i VFA-produktion. Det vanligast förekommande VFA som produceras efter att reaktorn stabiliserades var caproinsyra (50%), följt av ättiksyra (23%) och smörsyra (20%). Högre mängd ammoniumkväve (1,3 till 14,32 mg/g VS) jämfört med löslig fosfor (0,69 till 7 mg/g VS) erhölls under samjäsningsprocessen. Förlusten av VFA på grund av produktion av metan minskade markant eftersom pH i reaktorn justerade sig själv i intervallet 5 – 5,7. Batchjäsningsexperiment genomfördes i 15 dagar med användning av endast primärslam, endast matavfall och en blandning av primärslam och matavfall. Två inokulum med ursprung från en anaerob rötkammare och dels från pilotskalereaktorn användes i experimentet. Resultaten visade att VFA-produktion utan pH kontroll påverkas betydligt av vilket slags substrat och inokulum som används. Sammansättning av VFA påverkas mer av vilket slags inokulum som användes jämfört med vilket substrat som används. Sammanfattningsvis visar resultatet av denna studie att det finns potential för att producera VFA genom samjäsning av primarslam och matavfall utan pH kontroll.
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Bergh, Alexandra Jane. "Characterisation of the sensory profile of Cyclopia intermedia and optimisation of fermentation parameters for improved product quality". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/95908.
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Thesis (MScFoodSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: In light of the limited and inconsistent supply of good quality honeybush tea, a species-specific sensory profile and the physicochemical characteristics of Cyclopia intermedia (honeybush) tea were determined to ultimately establish the optimum fermentation parameters for this herbal tea on laboratory-scale and to validate these findings on commercial-scale. The characteristic sensory profile of C. intermedia can be described as sweet tasting and slightly astringent with a combination of “fynbos-floral”, “fynbos-sweet”, “fruity” (specifically “apricot jam”, “cooked apple”, “raisin” and “lemon/lemon grass”), “woody”, “caramel/ vanilla” and “honey-like” aromas. The flavour can be described as distinctly “fynbos-floral”, “fynbos-sweet” and “woody”, including hints of “lemon/lemon grass” and “hay/dried grass”. The results of the sensory study were used to create a C. intermedia sensory wheel and lexicon, and an elementary grading system that categorised samples into “good”, “average” and “poor” sensory quality was proposed. Physicochemical parameters, i.e. soluble solids (SS) content, absorbance as a measure of colour, and turbidity, were evaluated as possible rapid predictors of sensory quality. High SS content, absorbance and turbidity correlated strongly with “poor” sensory quality. A linear relationship existed between the physicochemical parameters. The effect of fermentation temperature (70, 80 and 90°C) and time (12, 16, 24, 36, 48 and 60 h) on the sensory and physicochemical characteristics of C. intermedia was determined on laboratory-scale. Increasing fermentation time increased the intensity of positive sensory attributes, while decreasing the intensity of negative sensory attributes. The SS content, colour and turbidity of infusions decreased with increasing fermentation time, while the SS content and turbidity of infusions increased with increasing fermentation temperature. Fermentation at 90°C for 36 h on laboratory-scale produced C. intermedia with the best sensory properties, while preserving the SS content and colour of infusions. Fermentation at 70°C and 80°C required longer fermentation times for development of positive sensory attributes. Fermentation at 90°C was subsequently validated on commercial-scale. Laboratory-scale fermentation of the same batches of plant material was also carried out concurrently to allow direct comparison of the scale of fermentation on tea quality. Commercial-scale fermentation, despite increased variability as a result of increased batch volumes and heating difficulties, produced C. intermedia of “good” sensory quality after 24 and 36 h of fermentation. Increasing fermentation time had little effect on the SS content and colour of infusions of tea produced on commercial-scale, but turbidity increased significantly after 36 h. Thus, to produce C. intermedia with consistently good quality on commercial-scale, fermentation at 90°C for 24 to 36 h is recommended. Increasing fermentation time past 48 h should be avoided to prevent turbidity and the development of sensory attributes characteristic of over-fermented tea. However, due to the large variability of commercial-scale honeybush tea production, it is recommended that each batch be monitored between 24 and 36 h to determine when optimum fermentation has been obtained.
AFRIKAANSE OPSOMMING: Beperkte en wisselvallige beskikbaarheid van goeie gehalte heuningbostee noodsaak die optimisering van fermentasie parameters vir Cyclopia intermedia. Optimisering van fermentation parameters is op laboratorium skaal gedoen, gevolg deur validasie van die parameters op kommersiële skaal. Vooraf is die spesie-spesifieke sensoriese profiel en die fisies-chemiese eienskappe van C. intermedia tee bepaal. Die kenmerkende sensoriese profiel van C. intermedia kan beskryf word as soet en effens vrank met 'n kombinasie van "fynbos-blomagtige", "fynbos-soet", "vrugtige" (spesifiek "appelkooskonfyt", "gekookte appel", "rosyntjie” en “suurlemoen/sitroen gras"), "houtagtige", "karamel/vanilla" en "heuningagtige" aromas. Die smaak kan beskryf word as "fynbos-blomagtig", "fynbos-soet" en "houtagtig", met 'n tikkie "suurlemoen/sitroen gras" en "hooi/gedroogde gras". Die resultate van die sensoriese studie is gebruik om 'n C. intermedia sensoriese wiel en leksikon, asook 'n basiese graderingstelsel wat tee monsters in "goeie", "gemiddelde" en "swak" sensoriese kwaliteit klassifiseer, te ontwikkel. Fisies-chemiese parameters: oplosbare vastestof (SS) inhoud; absorbansie as 'n maatstaf van kleur; en troebelheid, is geëvalueer as moontlike indikasies van sensoriese kwaliteit. Hoë SS inhoud, absorbansie en troebelheid waardes het sterk met "swak" sensoriese kwaliteit gekorreleer. 'n Lineêre verwantskap bestaan tussen die fisies-chemiese parameters en kwaliteit. Die effek van fermentasie temperatuur (70, 80 en 90°C) en -tyd (12, 16, 24, 36, 48 en 60 h) op die sensoriese en fisies-chemiese eienskappe van C. intermedia is op laboratorium skaal bepaal. Verlenging van fermentasie tyd het die intensiteit van die positiewe sensoriese eienskappe verhoog, terwyl dit die intensiteit van negatiewe sensoriese eienskappe verminder het. Die SS inhoud, kleur en troebelheid van die tee het met verlengde fermentasie tyd afgeneem, terwyl die SS inhoud en troebelheid met verhoging van fermentasie temperatuur toegeneem het. Fermentasie by 90°C vir 36 h op laboratorium skaal het tee met die beste sensoriese eienskappe geproduseer, met behoud van die SS inhoud en kleur. Fermentasie by 70°C en 80°C het 'n langer fermentasie tyd vir die ontwikkeling van positiewe sensoriese eienskappe vereis. Fermentasie by 90°C is daaropvolgens op kommersiële skaal uitgevoer, met gelyktydige laboratorium skaal fermentasie van dieselfde plantmateriaal lotte om die direkte effek van die skaal van fermentasie op tee kwaliteit te bepaal. Kommersiële fermentasie, ten spyte van verhoogde wisselvalligheid as gevolg van groot volumes tee en probleme met verhitting, het tee van "goeie" sensoriese kwaliteit na fermentasie periodes van 24 en 36 h geproduseer. Verlenging van fermentasie tyd het min uitwerking op die SS inhoud en kleur van kommersiel gefermenteerde tea gehad, maar troebelheid het beduidend na 36 h toegeneem. Fermentasie by 90°C vir 24 - 36 h word gevolglik aanbeveel om tee met goeie gehalte op kommersiële skaal te produseer. Fermentasie vir langer as 48 h moet vermy word om troebelheid te voorkom en die ontwikkeling van sensoriese eienskappe kenmerkend van oor-gefermenteerde tee te vermy. As gevolg van faktore wat groot variasie in kommersiële skaal heuningbostee produksie kan teweegbring, word aanbeveel dat elke produksielot tussen 24 en 36 h gemonitor word om die optimum fermentasie tyd te bepaal.
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Mackintosh, E. D. "The effect of monensin on in vitro rumen fermentation and in vivo rumen and total tract digestion and milk production in the dairy cow". Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265711.
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Gagné, Isabelle. "Enhanced high-fructose syrup production by an hybrid fermentation/pervaporation system using a silicone rubber hollow fiber membrane module". Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9361.
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In this study, a mutant of the yeast Saccharomyces cerevisiae was used for the selective conversion of glucose to ethanol using feed solutions of sucrose. Batch fermentation using 30% (w/v) sucrose without membrane separation of ethanol required about 27 hours for glucose to be decreased to 2% (w/v), with a fructose yield of 99%, and an ethanol yield of 78%. Batch fermentation using 30% (w/v) sucrose with membrane separation of ethanol required about 16.5 hours for glucose to be decreased to 2% (w/v), with a fructose yield of 96.5% and an ethanol yield of 79.5%, if the membrane was started after 6 hours of batch mode. The process required about 15 hours if the membrane was started after 3 hours of batch mode, with a fructose yield of 92%, and an ethanol yield of 82%. In fed-batch mode the yeast was able to process the equivalent of a 40% (w/v) sucrose feed in 24 hours, compared to well over 40 hours without ethanol removal, with yields of, 98% fructose, and 82% ethanol. (Abstract shortened by UMI.)