Call number: LD2668 .T4 1985 C64 / Master of Science

Submitted in fulfilment for the requirements for the degree of Doctor of Technology: Biotechnology, Durban University of Technology, 2010. / South African edible oil processing plants produce approximately 3 x 105 tonnes of oil annually with up to 3 tonnes of water for every tonne of oil produced. Wastewater that contains oil extracts varies in organic loading from 30,000 to 60,000 mg.l-1 COD. This wastewater can be used to grow oleophilic fungi to produce valuable industrial products. The global vitamin B market is approximately R25.5 billion with 4500 metric tonnes being produced. A large proportion of this is produced using the fungus Eremothecium gossypii using oil substrates. The aim of this study was to to develop a novel method to produce riboflavin with the aid of fungi, using edible oil effluent (EOE) as substrate, and to optimize the production thereof by statistical experimental design. Four fungi were surveyed for their growth potential on EOE and two, E. gossypii (CBS109.51) and C. famata (ATCC 208.50) were found to produce sufficient riboflavin for further study. Mutation of these organisms using ethylmethane sulphonate (EMS) increased riboflavin production from 3.52 mg.l-1 to 38.98 mg.l-1, an 11-fold increase. An enzyme pathway responsible for this was found to involve isocitrate lyase and comparison of this enzyme’s activity in the mutant against the wild-type using Michaelis-Menten kinetics showed a higher reaction velocity (Vmax) with a reduced substrate affinity (Km) indicating that the mutation was associated with this enzyme. Biomass comparisons were fitted to the sigmoid Gompertz model which was used to compare the wild-type to the mutant and increased specific growth rates and doubling times were observed in mutated cultures of E. gossypi. A strategy of statistical experimental design was pursued to optimize media components and iterative fractional factorial experiments culminating in a central composite optimization experiment were conducted. Statistically verified mathematical models were developed at each stage to identify important media components, predict media interactions, show directions for improvement and finally, predict maximum riboflavin production. An eight-factor resolution IV fractional factorial increased riboflavin production to 112 mg.l-1 followed by a four-factor resolution V experimental design which increased riboflavin production to 123 mg.l-1. A two-factor (yeast extract and NaCl) central composite experimental design predicted a maximum riboflavin production of 136 mg.l-1 which was a 3.5-fold increase from the mutant, and 38.6-fold higher than the E. gossypii wild-type. The optimized value was achieved within predicted confidence intervals in confirmatory experiments. Cost implications for production of riboflavin on EOE were calculated and a 10% technology uptake by the edible oil industry could yield a riboflavin industry with a 63.65 million rand turnover and a potential 24.96 million rand gross profit margin. / National Research Fund.

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This thesis investigates whether fats, akin to other taste stimuli, exhibit sensory properties such as mixture interactions. In order to determine gustatory, rather than tactile or olfactory effects, viscosity-controlled emulsions of deodorised oils were used as the base to which taste stimuli were incorporated and presented to a panel of trained assessors. In preliminary qualitative assessments, panellists described the 10% olive oil emulsion as saltier, stronger, fattier and having a more lingering aftertaste than the non-oil control, suggesting that oil modulates taste duration as well influencing taste intensity and/or perceived quality. Panellists were unable to rate the oil/fat taste per se with any degree of certainty hence further experiments examined the effect of oil on the perception of taste mixtures. In mixture interaction experiments, the addition of oil did not result in mixture suppression or enhancement for sweet, salty, sour or bitter while it significantly enhanced umami. To determine the locus of interaction, when MSG and oil were presented to each side of the tongue separately, the enhancement effect disappeared indicating a peripheral mechanism of interaction, similar to the attenuation of chilli burn by oil. In contrast, suprathreshold sucrose sweetness was enhanced by the contralateral presentation of oil, indicating sensory processing at a higher locus. Furthermore, the addition of oil significantly reduced bitterness in a caffeine-MSG mixture. Since earlier experiments did not indicate any interaction between oil and bitterness, the decrease in the perceived bitterness of this binary mixture is attributed to an increase in umami which is likely to have suppressed bitterness, the perceptually dominant component in this mixture. These findings suggest a gustatory role for fats in modulating the taste profile of mixtures, in particular, enhancing total taste intensity, prolonging taste duration, and enhancing umami. A taste receptor-based model of fat perception provides for an orosensory mechanism capable of signalling the arrival of the most energy-dense nutrient, essential fatty acids and fat-soluble vitamins. The chemosensory signal may also be the basis for hedonic responses with subsequent implications for intake.

Thèse : Sciences : Université, Faculté des sciences de Paris : 1855. / Titre provenant de l'écran-titre.

published_or_final_version / Botany / Master / Master of Philosophy

Fourier transform near-infrared (FT-NIR) spectroscopy was investigated as a means of quantitative analysis of edible fats and oils. Initially, a method of simultaneously determining the cis and trans content, iodine value and saponification number of neat fats and oils using a heated transmission flow cell was developed. Two partial least squares (PLS) calibrations were devised, a process-specific calibration based on hydrogenated soybean oil and a more generalized calibration based on many oil types, the latter able to analyze oils from a variety of sources accurately and reproducibly. Methodology for the quantitative determination of the peroxide value (PV) of edible oils using a novel glass-vial sample handling system was subsequently developed, based on the stoichiometric reaction of triphenylphosphine with hydroperoxides to form triphenylphosphine oxide. The PV calibration was derived using PLS regression, and the results of a validation study demonstrated that PV could be quantitated accurately if a normalization routine was used to compensate for the inherent dimensional variability of the vials. The vial sample handling system was then used in the development of PLS IV calibrations for the process analysis of commercial oil samples, and these samples were also used to evaluate a global IV calibration devised by Bomem Inc. The discriminant features available through PLS were shown to enhance the accuracy of the IV predictions by facilitating the selection of the most appropriate calibrations based on the spectral characteristics of closely related oils. The predictions obtained using the global IV calibration provided clear evidence that a generalized calibration based on a large and varied selection of oils could provide a means of IV determination by FT-NIR spectroscopy. Subsequently, a generalized FT-NIR trans calibration was developed and shown to yield trans values that were in good agreement with those obtained by the AOCS mid-FTIR single-bounce hori

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.

Color formation in oils during frying is one of the most noticeable degradation reactions that occur in the frying oil. Degradation reactions cause formation of products that positively and negatively impact the nutritional and sensory qualities of both the food being fried and the frying oil. The origins of these pigment forming reactions in the oil and the factors affecting these reactions are not well understood. Assessments of the mechanisms, the components involved and external conditions affecting oil darkening were conducted. The effect of basic food ingredients, commercially sold and laboratory formulated breading and battering, preformed lipid hydroperoxides and phospholipids on color formation and oil degradation of the frying oil were investigated. Protein products, specifically whey protein, caused both the fastest darkening and thermo-oxidative deterioration of the frying oil. This breakdown was aided further through the addition of minor food materials such as glucose and amino acids as well as lipid hydroperoxides in concentrations greater than 5 % of the frying oil. Nonenzymatic browning is the main reaction causing color formation in the frying oil and utilizes carbonyls from the food product such as starches, sugars and lipid oxidation products as starting materials alongside amino groups from proteins and amino acids. Breading ingredients contributed to oil color formation due to particles from the food crust breaking off into the frying oil to further accelerate browning reactions. Increasing the temperature of the frying oil provided additional stimulus for color forming and thermo-oxidative reactions to progress at a faster rate. / xv, 184 leaves : ill. ; 29 cm