Dissertations / Theses on the topic 'Edible Oxidation'

This thesis describes the use of a novel chemiluminescence (CL) technique to deter·mine the extent of oxidation and stability in both model compounds and vegetable oils. As it is the presence of hydroperoxides in vegetable oils that leads to theirdeterioration, the hydroperoxides of methyl linoleate (MU were used as model compounds in a CL study of hydroperoxide decomposition in nitrogen, both in the bulk and on active substrates. The largest signals and the fastest decays occurred on neutral alumina. The results indicate induced decomposition via a bimolecular initiation of hydroperoxides adsorbed on adjacent active sites. The majority of these hydroperoxides are vertical to the surface, being bound to the alumina through the ester group only. A relationship was found between hydroperoxide concentr·ation and initial intensity when the methyl linoleate hydroperoxide was adsorbed on neutral alumina. Solutions of natural and arti-ficial antioxidants in ML were studied. Some solutions gave changes in kinetics. These changes suggest that the antioxidant itself may contribute to the CL. The method of inhibitors was used to find the rate of initiation and hydroperoxide level in ML at 80c:>C. The spectral distribution of CL was determined for model compounds, antioxidants and vegetable oils. In the presence of antioxidants ther-e was a shift towar-d the r-ed end of the spectr-um. In model compounds, the CL was most likely due to an excited triplet state ketone and this is consistent with the mechanism for- ter·mination of alkyl peroxy r-adicals. The techniques developed for the model compounds were extended to the mor-e complex vegetable oils. Unrefined and deliberately damaged vegetable oils were studied at 80c:>C on neutral alumina. CL examination of these oils in nitr-ogen was able to distinguish between some damaged and undamaged oils. Conjugated diene levels did not correlate well with CL results. 0<-tocopherol and a-carotene were found to be chemiluminescent on alumina and their presence in unr·efined oil may inter·fer·e with CL assessment. The method of inhibitors, when applied to a vegetable oil sample, permitted the determination of both hydroperoxide concentration and the level of natural antioxidant alr-eady present in the oil. ii

A novel and rapid method was developed to monitor the autoxidation of edible oils by Fourier transform infrared (FTIR) spectroscopy with the use of disposable polymer infrared (PIR) cards having a microporous polytetrafluoroethylene (PTFE) sample substrate. Under conditions of mild heating (~58°C) and aeration, both model triacylglycerols (TAGS) and edible oils applied onto the PIR cards underwent rapidly accelerated oxidation. In order to compare the oxidative stability of samples on the PIR cards in terms of the time required to reach a peroxide value (PV) of 100 mequiv/kg oil, matching the end-point measured in the standard active oxygen method (AOM), an absorbance slope factor (ASF) was determined to relate changes in hydroperoxide (ROOH) absorbance (peak maximum found within the range of 3500--3200 cm-1 ) to PV. Similar ASF values were found for the four edible oils tested (safflower, canola, sunflower, and extra virgin olive oil), permitting determination of a pooled, universally applicable ASF value of 0.0526 mAbs/PV.

O presente trabalho teve como objetivos principais utilizar reações enzimáticas para a degradação de resíduos de laboratório e na síntese de álcoois quirais. Na primeira parte foi realizada uma triagem de microrganismos e enzimas hidrolíticas, objetivando a biorreciclagem de hexano presente no resíduo contendo uma mistura hexano-acetato de etila. Esta mistura é largamente utilizada para purificação de compostos químicos por cromatografia líquida. O método de biorreciclagem consistiu na hidrólise enzimática do acetato de etila, viabilizando, dessa forma, a recuperação do hexano puro de forma simples e rápida, pois os produtos dessa reação são altamente solúveis na fase aquosa. Na segunda parte do trabalho, avaliamos o potencial catalítico de diversas plantas comestíveis em reações orgânicas de óxido-redução visando à síntese enantiosseletiva de álcoois quirais. As reações escolhidas, para tal propósito, foram a redução de cetonas pró-quirais e a resolução cinética de álcoois via oxidação enantiosseletiva. Em muitos casos, os enantiômeros foram obtidos, separadamente, com pureza enantiomérica de até 99% dependendo da planta utilizada como biocatalizador.
The present work had as main goals the use of enzymatic reactions to degrade laboratory residues and to synthesize chiral alcohols. In the first part, it was carried out a screening of microorganisms and hydrolytic enzymes aiming the biorecycling of hexane from laboratory residues (a mixture of hexane-ethyl acetate). This misture is widely employed to purify chemicals by liquid chromatography. The biorecycling consists of enzymatic hydrolysis of ethyl acetate in a biphasic system. Due to the high solubility of the undesired products from this reaction in the aqueous phase, the hexane was easily recovered. To evaluate the possibility of treatment of effluents in a high amount, we carried out the biorecycling in a continuous system with tubular reactor using immobilized lipase (Novozyme 435). By the use of this system, the hydrolysis ratio was around 70% with no lost of enzyme stability along 6 hours work. In the second part of the work, we evaluated the catalytic potential of several edible plants in oxido-reduction reactions aiming the enantioselective synthesis of chiral alcohols. The chosen reactions were the reduction of prochiral ketones and the kinetic resolution by enantioselective oxidation. In several cases, depending of the plant employed as biocatalyst, the (R) or (S)- enantiomer were obtained in high enantiomeric purity (up to 99%). For example, the Arracacia xanthorrhiza B. (mandioquinha) performed an efficient enantioseletive reduction of 1-(4-bromophenyl)ethanone to the (S)-1-(4-bromophenyl)ethanol with 98% e.e. (enantiomeric excess), while the a Manihot esculenta (mandioca) gave the (R)-1-(4-bromophenyl)ethanol with 90% e.e. Some plants showed a good oxidative performance. For example, Coriandrum sativum L. (coentro) gave the quantitative oxidation of 1-(4-methyphenyl)ethanol to the 1-(4-metilphenyl)ethanona.

Lipid oxidation has important consequences in the edible oil industry, producing compounds with sensory impact and thus reducing the economic value of the products. This work focused on the development of two Fourier transform infrared (FTIR) spectroscopy methods for the measurement of peroxide value (PV) and anisidine value (AV), representing the primary and secondary oxidation products of edible oils.
The infrared method developed for PV determination was based on a mathematical treatment by the partial least squares method of the information contained in the spectral region between 3750 and 3150 cm$ sp{-1}$.
The second method developed considered aldehyde content and anisidine value, a measure of secondary oxidation products.
The two methods developed are rapid ($ sim$2 min/sample) and have the advantage of being automatable. An infrared system coupled to a computer can collect the spectrum of an oil, analyze it and present a report without the need for personnel trained in FTIR spectroscopy. The cost of such a system would rapidly be absorbed through savings on personnel cost, time and chemical reagents required for conventional chemical methods and as such provides a useful advance in quality control methodology for the edible oils sector. (Abstract shortened by UMI.)

Les huiles végétales comme les huiles de cameline et tournesol sont des sources d’acides gras polyinsaturés bon pour la santé mais également très sensibles à la dégradation oxydative. Ce travail vise à améliorer la stabilité oxydative d’huiles alimentaires (principalement l’huile de cameline) via l’incorporation de composés phénoliques antioxydants soit comme composé pur (quercétine) soit comme un mélange plus complexe extrait à partir d’un coproduit de la noix. La faible solubilité de la quercétine dans l’huile a été contournée avec succès par le développement d’une voie d’enrichissement sans solvant en présence de phospholipides. Ainsi, la formulation à base de quercétine-phospholipides a permis d’augmenter significativement à la fois la solubilité de la quercétine and la stabilité oxydative de l’huile. Cette stabilité oxydative, mesurée par vieillissement accéléré à chaud, s’est révélée variable selon les concentrations en quercétine et phospholipides. L’hypothèse du rôle central des associations colloïdales dans ces observations a été formulée. Des données sur la solubilité de la quercétine dans différents solvants d’intérêt industriel ont également été générées. Pour les extraits phénoliques à base de tourteau de noix, en plus de l’amélioration de la stabilité oxydative, les paramètres influençant l’extraction ont été identifiés et une modélisation des procédés batch et semi-continu proposée. L’effet protecteur contre l’oxydation de l’huile d’un extrait de noix présentant une haute activité antiradicalaire s’est révélé dose-dépendant et a permis un accroissement significatif de la durée de conservation des huiles enrichies
Vegetable oils like camelina and sunflower oils are sources of healthy polyunsaturated fatty acids that are however highly susceptible to oxidative degradation. This work aimed at enhancing the oxidative stability of edible oils, mostly camelina oil by incorporating phenolics antioxidants, either as a pure component, quercetin, or as a more complex mixture extracted from a walnut by-product. The low solubility of quercetin in oils was successfully circumvented by developing a solvent-free route of enrichment in presence of phospholipids, so that quercetin-phospholipids formulation allowed to significantly increase both quercetin solubility and the oxidative stability of the oils. The enhanced oxidative stability, monitored under accelerated conditions of heating, was found to vary according to quercetin-phospholipid concentrations and ratios, and it was assumed that colloidal associations played a key role in the enhancement. Data of quercetin solubility in various solvents of industrial interest were also provided. For phenolic extract recovered from a walnut press-cake in addition to oxidative stability enhancement, modelling of batch and semi-continuous extractions was performed and influent parameters were identified. The protective effect against lipid oxidation of a walnut extract exhibiting high antiradical activity was dose-dependent and significantly extended the shelf life of enriched oils

Si les lipides contribuent à la valeur nutritionnelle et sensorielle de nombreux aliments, ils sont particulièrement sensibles aux réactions d'oxydation. Les principaux mécanismes mis en jeu lors de l'oxydation des acides gras insaturés sont relativement bien connus. En revanche, il est aujourd'hui quasiment impossible de prédire l'avancement des réactions et souvent nécessaire de recommencer une nouvelle étude de stabilité oxydative pour tout nouveau couple produit alimentaire / procédé de transformation. L'objectif de la thèse est donc de construire un modèle mécanistique couplé à un modèle de transfert de l'oxygène dans le but de prédire l'avancement des réactions d'oxydation dans un milieu lipidique continu et dans des conditions expérimentales définies et contrôlées (température, oxygénation, composition en acides gras, composition en antioxydants). Pour cela, un schéma réactionnel visant à détailler l'ensemble des réactions impliquées dans le phénomène d'auto-oxydation des lipides a été proposé puis un modèle stoechio-cinétique a été construit à partir des valeurs des paramètres cinétiques issues de la littérature. La réactivité des acides gras insaturés présents dans trois huiles végétales d'usage courant (colza, tournesol, tournesol oléique), purifiées de leurs antioxydants naturels, a été étudiée entre 80 et 180°C, en suivant différents marqueurs d'oxydation (diènes conjugués, hydroperoxydes, aldéhydes, polymères). Comme attendu, les cinétiques d'oxydation se sont avérées dépendantes de la composition des huiles en acides gras, de la température et des conditions d'oxygénation. L'ajout d'antioxydant(s) a confirmé l'effet protecteur de l'α-tocophérol, qui n'a pas été amélioré par un enrichissement en acide chlorogénique, acide phénolique naturellement présent dans les graines de tournesol. Les résultats obtenus ont été utilisés pour valider le modèle développé, dont les prédictions permettent de reproduire les tendances expérimentales. Deux limitations ont été mises en évidence au cours de cette phase de validation dont la première concerne la description fiable et précise du mécanisme d'oxygénation du milieu, qu'il sera nécessaire de mesurer dans une huile à haute température pour valider le modèle d'oxydation. Par ailleurs, compte tenu du nombre important de réactions prises en compte, il sera indispensable de disposer d'un jeu de données expérimentales plus important, pouvant inclure des intermédiaires radicalaires. Pour cela, les potentialités de la résonance paramagnétique électronique ont été étudiées au cours de ce travail, à la fois pour suivre les radicaux lipidiques et pour accéder à des paramètres cinétiques pour des réactions radicalaires, peu disponibles dans la littérature.

The present study sought for practical ways to improve the frying performance of oils without compromising the availability of the essential fatty acids and nutraceuticals. To this end, the influence of temperature, oxygen concentrations, and compositions of minor components on frying performance was investigated. A novel frying protocol, utilizing carbon dioxide blanketing, was developed and found to significantly improve the performance of the frying oil. Optimizing both the amounts and the compositions of endogenous minor components also improved the performance of the frying oil. Twenty one novel antioxidants were synthesized and evaluated under frying and storage conditions. Antioxidant formulations consisting of a combination of endogenous and synthesized antioxidants were developed and tested in an institutional frying operation. A rapid and effective frying test was developed to assess the frying performance of oils and applied antioxidants. Furthermore, a novel procedure for direct hydroxynonenal analysis in frying oil was developed.
xx, 249 leaves; 29 cm

La friture profonde de type batch a été étudiée dans le projet FUI Fry’In (Réf. AAP17, 2014-2018) dans le but de proposer des innovations de rupture pour des friteuses batch domestiques et professionnelles. La thèse a appuyé le projet sur la maîtrise de deux effets négatifs de la friture : i) la thermo-oxydation de l’huile responsable des mauvaises odeurs et produits de dégradation ainsi que ii) la prise d’huile généralement favorisée au détriment de son égouttage. L’étude a été réalisée en combinant des mesures directes (spectroscopie et imagerie infrarouges en mode ATR, photo-ionisation, mesures DSC, imagerie rapide…) et modélisation multi-échelle (écoulement de l’huile et égouttage lors du retrait, description lagrangienne des réactions en présence d’un écoulement, couplage avec les ciné-tiques de dissolution de l’oxygène). La complexité du processus de thermo-oxydation a été réduite en considérant les hydroperoxydes comme une forme de stockage organique de l’oxygène, qui propage l’oxydation dans des régions en anoxie. Leur décomposition produit de nombreux composés de scission, dont la nature est influencée par les conditions locales de température et de concentration en oxygène. La prise d’huile a été décrite comme le bilan net entre l’huile charriée au moment du retrait et l’huile égouttée. L’égouttage a été étudié sur des barreaux métalliques et des produits réels. Il se conduit à la formation de quatre à huit gouttes en quelques secondes. Les cinétiques de drainage anisothermes ont été prédites par un modèle mécanistique. Le mécanisme spécifique de prise d’huile en cours de friture a été aussi analysé ; il se produit uniquement dans le cas des produits préfrits congelés
Batch deep-frying has been investigated within the collaborative project FUI Fry’In (ref. AAP17, 2014-2018) with the aim of proposing breakthrough innovations for small and medium size appliances. The PhD thesis was part of the project and focused on two specific adverse effects of deep-frying on food products: oil thermo-oxidation responsible for break-down products and off-flavors, and oil pickup process usually favored relatively to oil dripping. The work was carried out by combing direct measurements (FTIR-ATR spectroscopy and imaging, photoionization, DSC measurements, fast imaging…) and multiscale modeling (oil flow and oil dripping during product re-moval, Lagrangian description of reactions in aniso-thermal flows, coupling with oxygen dissolution kinetics). The complex problem of thermo-oxidation was split into simpler mechanisms by noticing that hydroperoxides are a kind of long-lived form of or-ganic oxygen, which trigger propagation in deep re-gions under anoxia. Their decomposition lead to various scission products, which were shown to be in-fluenced by both local temperature and oxygen con-centration. Oil uptake was described as the net balance between the amount of dragged oil during product removal and oil dripping at the tips of the product. The dripping process studied on both metal-lic sticks and real products occurs in less than few seconds and leads to a formation of four to eight drop-lets. The detailed drainage kinetics in anisothermal conditions were captured and predicted with the pro-posed mechanistic models. The specific mechanism of oil uptake during the immersion stage was eluci-dated and was shown to occur only in parfried frozen products

The thermal, oxidative, and hydrolytic stability of several frying shortenings were studied via chemical, physical and sensory analyses. Corn, cottonseed and peanut oils, and cottonseed and soybean liquid shortenings were tested under static heating conditions, while peanut oil, and cottonseed and soybean oil liquid shortenings were evaluated under commercial frying conditions. The research had two objectives: to evaluate the relative stability of the various shortenings under both heating condition; and to evaluate new or modified quality assessment methods which would provide early prediction of heat abuse for the fast-food industry. Six of the conducted analyses were conventional or modified: free fatty acids; polar components; gas chromatograph volatile profiles; viscosity; FoodOil-Sensor; and sensory. Three were new: contact angle; high temperature; and high-temperature gas chromatographic analysis of triglyceride; and polar component % as determined by high-performance thin-layer chromatography (HPTLC). Under static heating conditions, varying heating periods or shortening types had significant (P<0.000l) effects on the resulting data of the following tests: free fatty acids; polar component; total volatiles; dielectric constant; viscosity; polar component % measured by HPTLC; contact angle; and sensory analysis; but heating time had no significant effect on triglyceride profiles Under commercial frying conditions of chicken nuggets and filets, heating time had significant effects on changes in the dielectric constant; free fatty acid %; viscosity; contact angle; and sensory rating; also it had a significant effect on the polar component % under chicken nugget frying conditions only. Furthermore, heating time had no significant effect on polar component % under chicken filet frying conditions and on polar component % by HPTLC under both frying conditions Cottonseed oil liquid shortening had sensory scores equal to peanut oil under static and commercial frying conditions even though peanut oil exhibited a greater chemical and physical stability. Soybean oil liquid shortening had an objective quality identical to peanut oil, however, its subjective quality was lower. Cottonseed oil liquid shortening had better flavor but less objective stability than soybean oil liquid shortening The cut-off quality level for the shortenings was not reached, because all the shortenings were discarded after seven days of use which was before the onset of significant-quality deterioration. The best on-site index of shortening stability was the FoodOil-Sensor reading (dielectric constant) which was followed by the free fatty acid test.
Ph. D.

Orientador: Célio Pasquini
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: A autoxidação de lipídeos é uma das principais causas de degradação de óleos e gorduras. Este processo gera uma série de compostos indesejáveis, tais como, peróxidos, hidroperóxidos e ácidos carboxílicos de cadeia curta. A determinação da estabilidade oxidativa de um óleo, é, portanto, essencial para estimar o tempo de prateleira - um parâmetro importante para a indústria alimentícia. Para quantificar o grau de oxidação de um óleo, uma série de parâmetros pode ser utilizada, como os índices de peróxido e de anisidina, o teor de dienos conjugados, dentre outros. Métodos acelerados foram desenvolvidos para a estabilidade oxidativa - uma medida da variação do grau de oxidação ao longo do tempo -, em particular o método Rancimat. Nele, uma amostra de cerca de 3 g de óleo e aquecida em temperaturas na faixa de 100-130 °C, e um fluxo de ar constante e passado através da amostra e carreado para um recipiente contendo água deionizada. O monitoramento da condutividade elétrica desta solução permite identificar o período de tempo necessário para que a taxa de formação de ácidos carboxílicos de cadeia curta se torne significativa. Este tempo é denominado tempo de indução (TI), e corresponde ao índice de estabilidade oxidativa (OSI - Oxidative Stability Index) do óleo. A espectroscopia de emissão no infravermelho próximo (NIRES), por outro lado, permite o monitoramento de hidroperóxidos, devido ao aumento e alargamento de uma banda em 2900 nm que ocorre ao longo do processo oxidativo. Neste trabalho foi desenvolvido e avaliado um fotômetro NIRES, dedicado para a determinação de estabilidade oxidativa. No método NIRES, uma amostra de 10 mL e aquecida a uma temperatura fixa (140 - 180 °C), sendo mantido um fluxo constante de ar purificado ao redor da amostra. A emissividade do óleo em 2850 e 2675 nm e continuamente monitorada com um detector de PbS, sendo a seleção dos comprimentos de onda realizada por dois filtros de interferência. A formação de hidroperóxidos ocasiona um aumento significativo da emissividade a 2850 nm, permitindo a determinação de TI de forma análoga ao método Rancimat.. O equipamento construído apresenta uma série de vantagens com relação ao método Rancimat, tais como: rapidez na análise, simplicidade operacional, menor consumo de amostra e a possibilidade de determinar a estabilidade oxidativa em temperaturas de fritura (140-180 °C). A precisão do método NIRES encontrada é equivalente à precisão do método Rancimat, e existe uma correlação entre eles (R = 0,90).
Abstract: Lipid autoxidation is the main cause of fats and oils deterioration. This process generates a series of undesirable compounds, such as hydroperoxides and low chain carboxylic acids. Thus, determination of oil fs oxidative stability is essential for estimation of the shelf life - an important parameter for the food industry. Several parameters are used for quantifying the degree of oxidation of an oil sample, such as the peroxide value, anisidine value, and conjugated dienes. Accelerated methods have been developed for measuring oxidative stability - the variation of the degree of oxidation with time -, particularly the Rancimat method. In this method, a constant air flow passes through a 3 g oil sample, heated at 110 - 130°C, and then is collected in a vessel containing deionized water. By monitoring the deionized water fs conductance, an induction time (IT) - which corresponds to the Oil Stability Index (OSI) - can be determined. On the other hand, near infrared emission spectroscopy (NIRES) allows the determination of IT by monitoring the formation of hydroperoxides. As the oil undergoes autoxidation, a band at 2900 nm becomes broader and more intense. In this work, a near infrared emission spectroscopy photometer, dedicated to determination of oxidative stability, has been developed and evaluated. In the NIRES method, a 10 mL oil sample is heated at a constant temperature (140 - 180 °C), and a purified air flow is maintained around the sample. The oil fs emissivity at 2675 and 2850 nm is continually monitored with a PbS detector, and the wavelengths are selected with two interference filters. Formation of hydroperoxides increases significantly the emissivity at 2900 nm, allowing the determination of IT in a way analogous to the Rancimat method. The developed equipment presents several advantages towards the Rancimat, including: faster analysis, lower sample consumption, operational simplicity, and the possibility of measuring oxidative stability at frying temperatures. Also, the method fs precision is equivalent to the Rancimat fs precision, and a correlation between them has been found (R = 0,90).
Mestrado
Quimica Analitica
Mestre em Química

Thesis (MSc Food Sc )--Stellenbosch University, 2002.
ENGLISH ABSTRACT: The oxidative stability of crude, cold-pressed mango kernel fat (MKF) was determined over a period of 240 days using the peroxide value (PV), conjugated diene value (CD) and p-anisidine value (AV) tests. The changes in fatty acid profile were monitored with gas chromatography and the oxidative status of MKF effectively predicted by FT-NIR spectroscopy. Results obtained from the different methods complemented each other and indicated the stable character of mango kernel fat against oxidative deterioration. The fatty acid profile constituted palmitic acid (CI6:0; 8.43%), stearic acid (CI8:0; 34.98%), oleic acid (CI8:1 cis; 48.05%), linoleic acid (CI8:2; 6.60%) and arachidic acid (C20:0; 1.73%). Trace amounts of C16:1 (0.56%), C18:1 trans (0.25%), C18:3 (0.43%), C20:1 (0.25%) and C22:0 (0.40%) were also found. The freshly pressed MKF had a peroxide value of 2.7 meq.kg", CD value of 0.07% and an AV of 2.2 mmol.kg", After 40 days of storage, the peroxide values of MKF stored with and without exposure to a limited amount of oxygen at 5, 15,25 and 40°C increased to 5 meq.kg" and 4 meq.kg" respectively. Emulsification of MKF had a stabilising effect (maximum PV = 2.8 meq.kg'), while exposure to UV light had a catalysing effect (maximum PV = 5 meq.kg'). These maximum values, decreased after 40 days. The CD values of MKF samples stored with and without exposure to oxygen at 5, 15,25 and 40°C increased to 0.18% and 0.16%, respectively at day 40. The CD values of samples exposed to light increased to 0_20% and the emulsified samples showed similar values to that of the MKF samples not exposed to oxygen. The conjugated diene values remained stable after day 40. The p-anisidine values of the MKF samples both stored with and without exposure to oxygen at 5, 15, 25 and 40°C varied between 0.5 and 5 mmol.kg". The weak correlation to the measurement of nonanal, as well as the low levels of 2-alkenals produced by the MKF, resulted in these low and sometimes non-linear values. The peroxide, conjugated diene and p-anisidine values obtained for MKF stored at 25°C over 240 days were low due to the low content of polyunsaturated fatty acids in MKF. This compared favourably with the higher values attained for sunflower, canola and olive oil, which are all rich in polyunsaturated fatty acids. The minimal changes observed in the fatty acid profile of mango kernel fat indicated the stability of the saturated fatty acids (CI6:0 and CI8:0) and oleic acid. In addition, the instability of linoleic and linolenic acids was evident due to oxidative deterioration. A decrease of 7.41% and 12.80% was observed between day 0 and 240 for the C18:2/C16:0 and C18:2/C18:0 ratios respectively. The prediction of the oxidative status of the MKF samples by near infrared spectroscopy were possible after the development of calibration models from a total data set of 300 samples of which one-third was used for independent validation. Principle component analysis (PCA) indicated classification at 0, 40 and the remaining (80 - 240) days. The best calibration model for PV yielded a SEP (standard error of prediction) of 0.46 meq.kg", correlation coefficient (r) of 0.95, bias of 0.02 and a root mean square error of prediction (RMSEP) of 0.46 meq.kg". The CD calibration model had a correlation coefficient of 0.89, SEP of 0.01 %, bias of 0.001 and RMSEP of 0.01% when developed on a data set with no pre-processing applied. The AV calibration had a SEP of 0.32 mmol.kg", bias of 0.03, RMSEP of 0.32 mmol.kg" and rof 0.93. The C18:2 and C18:3 models were built using partial least squares (PLS) regression and the values obtained for SEP were 0.31% and 0.054%, RMSEP 0.32% and 0.05%, bias 0.05 and 0.01 and correlation coefficcients were 0.82 and 0.54 respectively. The calibrations for CI8:1, C18:0 and C16:0 yielded weaker correlations. Good correlations were obtained when calibrating the CI8:2/CI6:0 and C18:2/CI8:0 ratios.
AFRIKAANSE OPSOMMING: Die oksidatiewe stabiliteit van ru, koud-geperste mango kern vet (MKV) (Mangifera indica L.) is oor 'n periode van 240 dae bepaal deur gebruik te maak van die peroksiedwaarde (PV), gekonjugeerde dieen waarde (CD) en p-anisidien waarde (AV) toetse. Die veranderinge in die vetsuurprofiel is gemonitor deur gaschromatografie en die oksidatiewe status van MKV is akkuraat voorspel word deur Fourier transformasie naby infrarooi (FT-NIR) spektroskopie. Die resultate van die verskillende toetsmetodes komplementeer mekaar goed en dui die stabiliteit van mango kern vet teen oksidatiewe verval aan. Die vetsuurprofiel is saamgestel uit palimitiensuur (C16:0; 8.43%), steariensuur (C18:0; 34.98%), oleïensuur (C18:1 cis; 48.05%), linoleïensuur (C18:2; 6.60%) en aragiedsuur (20:0; 1.73%). Spoorhoeveelhede C16:1 (0.56%), C18:1 trans (0.25%), C18:3 (0.43%), C20:1 (0.25%) en C22:0 (0.40%) is ook geïdentifiseer. Die vars geperste MKF het 'n peroksiedwaarde van 2.7 meq.kg", 'n CD waarde van 0.07% en 'n AV waarde van 2.2 mmol.kg" getoon. Na afloop van 40 dae opbergingsperiode by 5, 15, 25 en 40°C het die PV van MKV met 'n beperkte blootstelling aan suurstof na 5 meq.kg" vermeerder, terwyl die waardes van monsters sonder suurstofblootstelling na 4 meq.kg" vermeerder het. Emulsifisering van MKV het 'n stabiliserende effek (maksimum PV = 2.8 meq.kg") terwyl blootstelling aan ultraviolet (UV) lig 'n kataliserende effek (maksimum PV = meq.kgl ) op oksidasie gehad het. Hierdie maksimum waardes het na 40 dae afgeneem. Die CD waardes van MKF monsters opgeberg by 5, 15, 25 en 40°C en met beperkte blootstelling aan suurstof het vermeerder tot 0.18% terwyl die monsters sonder suurstofblootstelling by bogenoemde temperature vermeerder het tot 0.16% na 40 dae. Die gekonjugeerde dieen waardes van die monsters blootgestel aan UV lig het vermeerder tot 0.20%; terwyl die geëmulsifiseerde monsters waardes soortgelyk aan die MKV monsters sonder blootstelling aan suurstof getoon het. Gekonjugeerde dieen waardes het gestabiliseer vanaf dag 40. Die p-anisidienwaardes van MKV monsters opgeberg by temperature van 5,15, 25 en 40°C, met en sonder blootstelling aan suurstof, het varieer tussen 0.5 en 5 mmol.kg". Die swak korrellasie tussen nonanal produksie en p-anisidienwaardes, sowel as die klein hoeveelhede 2-alkenale geproduseer, was verantwoordelik vir hierdie lae en nie linêere waardes. Die peroksied, gekonjugeerde dieen en p-anisidienwaardes wat verkry is nadat MKV by 25°C in 240 opgeberg is, was laag weens die klein persentasie poli-onversadigde vetsure teenwoordig in die vet. Dit vergelyk goed met die hoë waardes wat verkry is vir sonneblom-, canola- en olyfolie wat almal ryk aan poli-onversadigde vetsure is. Die minimale veranderinge in die vetsuurprofiel van MKF dui op die stabiliserende invloed van versadigde vetsure (C16:0 en C18:0) en oleïensuur. Die onstabiliteit van linoleïen- en lineensuur duidelik uit hierdie vetsure se oksidatiewe verval. 'n Afname van 7.41% en 12.80% is waargeneem tussen dae 0 en 240 vir die C18:2/C16:0 en C18:2/C18:0 verhoudings, onderskeidelik. Die voorspelling van die oksidatiewe status van die MKF monsters met behulp van FT-NIR spektroskopie was moontlik deur die ontwikkeling van kalibrasie modelle. 'n Totale datastel van 300 monsters, waarvan ongeveer 'n derde vir validasie aangewend is, is gebruik vir die kalibrasiemodelle. Met behulp van PCA (hoojkomponent analise) kon drie klassifiseerbare groepe by 0, 40 en 80-240 dae onderskei word. Die beste kalibrasiemodel vir PV het 'n standaardfout van voorspelling (SEP) van 0.46 meq.kg", 'n korrellasiekoëffisient (r) van 0.95, 'n oorhelling van 0.02 en 'n standaardfout van voorspelling (RMSEP) van 0.46 meq.kg" gehad. Die CD kalibrasiemodel (geen voorafverwerking) het 'n r van 0.89, SEP van 0.01% oorhelling van 0.001 en RMSEP van 0.01% gehad. Die AV kalibrasie het 'n SEP van 0.32 mmol.kg', oorhelling van 0.03, RMSEP van 0.32 mmol.kg" en r van 0.93 gehad. Die C18:2 en C18:3 modelle is saamgestel deur PLS (partial least squares) regressie. Waardes verkry vir C18:2 en C18:3 was onderskeidelik: SEP 0.32% en 0.05%, RMSEP, 0.32% en 0.05%, oorhelling 0.05 en 0.01 en r 0.82 en 0.54. In die geval van C18:1, C18:0 en C16:0, het die kalibrasies swakker statistiek korrellasies getoon. Goeie korrellasies is verkry tydens kalibrasie vir die C18:2/C16:0 en C18:2/C18:0 verhoudings.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Edible oils are important sources of energy, fat soluble vitamins and essential fatty acids. However, their unsaturated fatty acids nature makes them highly susceptible to oxidative processes, making necessary the use of antioxidant additives. Synthetic antioxidants are widely employed by the industry, although there are several restrictions due to their adverse effects on human health. For this reason, this study investigated the antioxidant potential of 24 plant extracts: saffron (Crocus sativus L), rosemary (Rosmarinus officinalis), boldo (Peumus boldus Molina), white tea (Camellia sinensis (L.) Kutntze), mate tea (Ilex paraguariensis St. Hilaire), black tea (Camellia sinensis (L.) Kutntze), green tea (Camellia sinensis (L.) Kutntze), chamomile (Matricaria recutita L.), cinnamom (Cinnamomum zeylanicum), carqueja (Baccharis trimera (Less.) DC), lemon balm (Cymbopogom citratus), coriander (Coriandrum sativum L.), clove (Syzygium aromaticum), fennel (Foeniculum vulgare (Mill.) Gaertn), marjoram (Origanum majorana L.), basil (Ocimum basilicum), oregano (Origanum vulgare L. ssp Virens), senna (Cassia angustifólia), barbatimão (Stryphnodendron barbatimam Mart.), chapéu-de-couro (Echinodorus grandiflorus Mitch.), juca (Caesalpinia ferrea Mart. Ex Tul.), guarana (Paullinia cupana Kunth), pau d arco (Tabebuia serratifolia (Vahl) Nich.) and cat s claw (Uncaria tomentosa), by determining total phenolic content and antioxidant activity measured through the DPPH and FRAP assays. Thermogravimetric Analysis (TG), with both dynamic and isothermal (110 °C) analysis methods, was used to evaluate the thermal stability of the 24 plant extracts, as well as commercial antioxidants. Corn, soybean and sunflower oils, composed of unsaturated fatty acids, are widely used in Brazilian cuisine. Thus, antioxidant action of the extracts (rosemary, chamomile, coriander, fennel and senna) was also investigated by controlling the oxidative stability of edible vegetable oils when added to these, through the accelerated Rancimat methods, PetroOXY, PDSC and oven test. Clove extract showed the highest antioxidant capacity by FRAP assay and the best CFT. Extracts of juca and barbatimao, both from the Amazon Region, showed high TFC (133.63 ± 1.94 and 147.37 ± 1.99 mg GAE/g extract), confirming the excellent antioxidant capacity determined by the foregoing methods. The thermogravimetric profile of the extracts of cat's claw, saffron, rosemary, white tea and cinnamon stood out due to its good thermal resistance, indicating that may be used as antioxidant additives in formulations requiring heating. The rosemary extract applied to edible oils exhibited greater protective effect than other extracts tested, including the synthetic antioxidant BHT and TBHQ, when evaluated by the PDSC and PetroOXY methods. When the assessment was based on the Rancimat technique, its effect was similar to the one of BHT. Clove extract, although it is an excellent antioxidant, showed no thermal stability, with a mass loss of 81.4% in the first event (28.1 to 266.7 °C), due to the degradation of its main chemical constituent, eugenol.
Óleos comestíveis são fontes importantes de energia, vitaminas lipossolúveis e de ácidos graxos essenciais. Entretanto, a natureza insaturada dos seus ácidos graxos os torna altamente suscetíveis a processos oxidativos, tornando necessário o uso de aditivos antioxidantes. As indústrias de oleaginosas utilizam os de natureza sintética, todavia existem várias restrições quanto ao uso destas substâncias, devido aos efeitos nocivos atribuídos à saúde humana. Por estas razões, este trabalho investigou o potencial antioxidante de 24 extratos vegetais: açafrão (Crocus sativus L), alecrim (Rosmarinus officinalis), boldo-do-Chile (Peumus boldus Molina), chá branco (Camellia sinensis (L.) Kutntze), chá mate (Ilex paraguariensis St. Hilaire), chá preto (Camellia sinensis (L.) Kutntze), chá verde (Camellia sinensis (L.) Kutntze), camomila (Matricaria recutita L.), canela (Cinnamomum zeylanicum), carqueja (Baccharis trimera (Less.) DC), erva-cidreira (Cymbopogom citratus), coentro (Coriandrum sativum L.), cravo-da-Índia (Syzygium aromaticum), erva-doce (Foeniculum vulgare (Mill.) Gaertn), manjerona (Origanum majorana L.), manjericão (Ocimum basilicum), orégano (Origanum vulgare L. ssp Virens), sene (Cassia angustifólia), barbatimão (Stryphnodendron barbatimam Mart.), chapéu-de-couro (Echinodorus grandiflorus Mitch.), jucá (Caesalpinia ferrea Mart. Ex Tul.), guaraná (Paullinia cupana Kunth), pau d arco (Tabebuia serratifolia (Vahl) Nich.) e unha de gato (Uncaria tomentosa), através da determinação do conteúdo de fenólicos totais (CFT) (método Folin-Ciocateau) e da capacidade antioxidante aplicando os ensaios DPPH e FRAP. A análise Termogravimétrica (TG), pelos métodos dinâmicos e isotérmicos (110 °C) foi utilizada para avaliar a estabilidade térmica dos extratos vegetais e antioxidantes comerciais. Os óleos de milho, soja e girassol, constituídos de ácidos graxos insaturados, são muito utilizados na culinária brasileira. Assim, a ação antioxidante dos extratos (alecrim, camomila, coentro, erva-doce e sene) também foi investigada através do controle da estabilidade oxidativa de óleos vegetais comestíveis quando adicionados a estes, por meio dos métodos acelerados Rancimat, PetroOXY, PDSC e teste de estufa. O extrato de cravo exibiu o maior CFT e a melhor capacidade antioxidante pelo ensaio FRAP. Os extratos de jucá e barbatimão, oriundos da Região Amazônica, apresentaram altos CFT (133,63 ± 1,94 e 147,37 ± 1,99 mg EAG/g de extrato) confirmando a excelente capacidade antioxidante pelos métodos empregados. O perfil termogravimétrico mostrou que os extratos unha-de-gato, açafrão, alecrim, chá branco e canela destacaram-se por apresentar boa resistência térmica, indicando que podem ser utilizados como aditivos antioxidantes em formulações que necessitem de aquecimento. O extrato de alecrim aditivado nos óleos vegetais exibiu um efeito protetor superior aos demais extratos antioxidantes testados, inclusive aos sintéticos BHT e TBHQ quando avaliados pelos métodos PDSC e PetroOXY e efeito semelhante ao do BHT pela técnica Rancimat. O extrato de cravo, embora seja um excelente antioxidante, não apresentou estabilidade térmica, com perda de massa de 81,4% na primeira etapa (28,1 a 266,7 ºC), relativa à degradação do constituinte químico principal, o eugenol.

Les liens entre nutrition et santé sont étudiés depuis de nombreuses années et ont permis de démontrer que la consommation de certains aliments et nutriments pouvait avoir une action préventive sur le développement de certaines pathologies. En raison de leur structure particulière, les acides gras polyinsaturés (AGPI) vont jouer de nombreux rôles physiologiques au sein du corps humain et prévenir la survenue de nombreuses maladies. Toutefois, les français sont encore trop peu nombreux à en consommer en quantité suffisante, privilégiant les aliments d’origine animale et transformés riches en acides gras saturés et trans, connus pour augmenter les risques de maladies cardiovasculaires. Dans le cadre de ce travail, nous nous sommes donc intéressés à un moyen de supplémenter des aliments en AGPI, tout en les protégeant des attaques environnementales. En effet, en raison de la présence d’insaturations sur leurs chaînes carbonées, les AGPI sont extrêmement sensibles aux attaques oxydatives. Ainsi, une fois oxydés, les AGPI contenus dans les aliments vont induire la modification des propriétés organoleptiques, l’altération des qualités nutritionnelles ainsi que l’apparition de produits toxiques. L’objectif principal de ces travaux de thèse vise donc à proposer un moyen de stabiliser des huiles alimentaires riches en AGPI par co-encapsulation de ces huiles avec des antioxydants dans des microparticules constituées de biopolymères. Cette co-encapsulation permettra de préserver ces huiles de l’oxydation mais également d’encapsuler des antioxydants afin de renforcer la protection face à l’oxydation, d’administrer ce principe actif via l’alimentation et de le stabiliser
The links between nutrition and health have been studied for many years and have shown that the consumption of certain foods and nutrients could have a preventive effect on the development of certain pathologies. Because of their particular structure, polyunsaturated fatty acids (PUFAs) will play many physiological roles in the human body and prevent the occurrence of many diseases. However, the French are still too few to consume PUFAs in sufficient quantities, With a diet mostly based on foods of animal origin and processed products rich in saturated and trans fatty acids, known to increase the risk of cardiovascular disease. As part of this work, we were interested in a way to supplement foods With PUFAs, while protecting thern from environmental attacks. Indeed, because of the presence of unsaturations on their carbon chains, PUFAs are extremely sensitive to oxidative reactions. Thus, once oxidized, PUFAs contained in food will induce the change in organoleptic properties, the alteration of nutritional qualities and the appearance of toxic products. The main objective of these thesis works is thus to propose a way to stabilize fatty oils rich in PUFAs by co-encapsulating these oils With antioxidants in microparticles made of biopolymers. This co-encapsulation will preserve these oils from oxidation but also encapsulate antioxidants to enhance the protection against oxidation, administer this active ingredien via the diet and stabilize it

M. Tech. Mechanical Engineering.
Biodiesel, produced from the transesterification of vegetable oils or animal fats with simple alcohol in the presence of a catalyst, is well positioned to replace petroleum-based diesel. Biodiesel is a non-toxic, biodegradable and renewable fuel. Despite its advantages, the chemical nature of biodiesel makes it more susceptible to oxidation compared to mineral diesel during long-term storage. The production of Croton Oil Methyl Ester (COME), Moringa Oil Methyl Ester (MOME) and Jatropha Oil Methyl Ester (JOME) was therefore carried out. Also, a determination of the fuel related properties and investigation of oxidation stability of the methyl esters produced without and with antioxidants and its blends with mineral diesel were conducted. The results showed that most of the measured fuel related properties of produced methyl esters fulfilled the minimum requirements of EN 14214 and ASTM 6751 biodiesel standards. However, COME and MOME did not meet EN 14214 oxidation stability standards (6 h) while JOME displayed very high oxidation stability (10.43 h) well within specified oxidation stability standards. Overall, the biodiesel derived from non-edible oils of African origin such as COME, MOME and JOME can be utilized as a partial substitute for mineral diesel. This study recommends that PY and PG antioxidants be used for safeguarding biodiesel fuel from the effects of autoxidation during storage.

This study investigates the interplay of naturally occurring pro- and antioxidants during deep-fat frying. The study has significance to the food industry because knowledge of these interactions are important for maintaining the sensory and nutritional quality of fried food. Antioxidant protection was observed in an oil blend of sunflower, olive and butteroil when used for potato frying, reflecting the presence of butteroil. Fractionation of butteroil and incorporation of these fractions into heating studies showed enhanced stability in the liquid fraction. Carotenoids and tocopherols may be responsible for this protection since these natural antioxidants are present in butteroil and are known to migrate to the liquid phase during fractionation. When butteroil was blended with sunflower oil and stored at 37$\sp\circ$C no antioxidant activity was observed, suggesting that the high temperatures of frying may also be necessary in the observed protection, i.e. through the production of malliard reaction products. When the oil blend was used to fry cod and analyzed for oxidation by polymer formation, the oil showed less polymers than expected, in comparison to the extensive oxidation reported by change in dielectric constant and fatty acid analysis. Subsequent studies suggest that polymers produced during the frying of cod may preferentially bind to the fish protein. When the cod was freeze-dried prior to frying, the fish was shown to protect the oil against oxidation. Lipid and non-lipid solid fractions of the fish exhibited antioxidant protection under similar conditions. This suggests that phospholipids and protein, the primary components of the lipid and solid fractions, respectively, may be responsible for this protection. Enhanced stability of sunflower oil was also observed when commercial amino acids and phospholipids were incorporated and heated at 185$\sp\circ$C. The oxidative process of oils during deep-fat frying can be very complex. A wide variety of factors must be considered when determining the oxidative stability of a frying system. The competitive role of pro- and antioxidants potentially present in both the oils used for frying and the food substrates being fried can greatly influence the frying system and ultimately affect the quality of the food product.

by Shi Yuling.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (p. 159-184).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.

碩士
國立中興大學
農藝學系
89
Abstract The effect of paraquat-induced oxidative damage on membrane and protein in detached edible soybean (Glycine max L. cv Kaohsiung selection no.1) cotyledon and unifoliate leaves was investigated. Paraquat-induced oxidative strength increased with concentration and time. It was found to be effective in decreasing chlorophyll and protein levels, increasing lipid hydroperoxides, and then altered membrane permeability. Toxic oxygen radicals generated by paraquat rapidly react with membrane components and led to major electrolyte and solute leakages, decreased markedly total sugar, amino acids, ascorbate, glutathione, and thiol content in treated leaves. Vital fluorescent dyes, fluorescein diacetate also supports the membrane integrity changes under paraquat-mediated oxidative damage. Paraquat treatment resulted in an increase in protein carbonyl content, and caused further degradation of oxidative protein. Using SDS-PAGE, it was found that paraquat induced both quantitative and qualitative changes in protein pattern. Although unifoliate leaves contain much of antioxidants, but unifoliate leaves were found to be more sensitive to paraquat-induced oxidative damage than cotyledon. Differential sensitivity to the oxidant paraquat may be partially attributed to the differences in tissue structure and cell components, or partially to the difference in antioxidant ability.

Nutritional factors with antioxidant properties, such as those contained in edible algae or green plants, might be implicated in protection against cancer development. Chlorophyll and other tetrapyrrolic compounds, structurally related to heme and antioxidant bile pigment bilirubin, belong to important candidate molecules, which might be responsible for these effects. Based on our studies demonstrating antiproliferative effects of S. platensis edible alga extract on experimental model of human pancreatic adenocarcinoma we investigated in detail the effect of chlorophyll occurring abundantly in this alga. Since only scarce data exist on the antiproliferative effects of chlorophylls, the aim of our study was to assess these effects. The study was performed on experimental models of human pancreatic and prostate cancer. The inhibitory effects of chlorophylls (chlorophyll a, chlorophyll b, chlorophyllin and pheophytin a) on cell proliferation and cell viability were investigated in in vitro studies. Chlorophylls reduced the mRNA expression as well as activity of hemeoxygenase in tested pancreatic cancer cells. Simultaneously, chlorophylls played an important role in redox environment of studied cancer cell lines including modulation of mitochondrial membrane potential, reactive oxygen species (ROS)...