Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2016. / Microbial spoilage has been reported in various food products and this has led to increased food, fruit and beverage losses, thereby threatening economic growth, food safety and security. Furthermore, statistics have shown that more than 30% of agricultural produce in developing countries, mostly in Africa, is lost owing to microbial spoilage. Beverages, food and fruits are predominant contributors to the South African export market. In recent years, contamination of these products resulting in spoilage has been a problem, although partial spoilage control has been achieved using chemical preservatives such as dimethyl dicarbonate, sodium benzoate, potassium sorbate, and sulphur dioxide (SO2). However, prolonged exposure to these chemical preservatives can cause human health problems such as skin and/or eyesight damage, muscle and stomach pain, cardiovascular disease and the impairment of brain function. To mitigate such health concerns, biologically benign alternatives are deemed suitable, providing the rationale for this study.

Kafirin, the prolamin protein of sorghum grain, could be extracted from the by-products of the sorghum processing industry and used to make films and coatings for food packaging, in particular to extend the shelf-life of fruits and nuts. Protein-based films can be an environment-friendly alternative to synthetic plastic packaging systems. However, the properties of protein-based films are generally inferior to those of synthetic plastics. Modification can alter the properties of protein-based films. In this project, the interaction between phenolic compounds and kafirin was investigated in relation to their potential to modify kafirin films. A range of phenolic compounds was tested in terms of their ability to bind and complex with kafirin in an in vitro binding assay. The protein-phenolic compound interaction was quantified by haze formation and colorimetric determination of total polyphenol bound. Ferulic acid, catechin and extracted flavonoids from condensed tannin-free sorghum did not complex with kafirin. Tannic acid (TA) and sorghum condensed tannins (SCT) complexed kafirin and formed haze. Thus, T A and SCT were selected as potential modifying agents for kafirin films. TA and SCT were added at up to 20% (w/w tannin to protein basis) during kafirin film casting. Both TA and SCT bound to kafirin in the film. Scanning electron microscopy showed that TA modified films were less porous; and the SCT modified films appeared more globular in structure than unmodified film. Modification with both tannins increased the tensile stress and Young's modulus and decreased the tensile strain of the kafirin films. Oxygen permeability of the modified films was decreased, but no change in the apparent water vapour permeabilty. The T9 of the films increased with increased modification level. SOS-PAGE, FT-IR and Raman spectroscopy were used to study TA and SCT interaction with kafirin. SOS-PAGE revealed a high Mr band for kafirin-SCT complexes which did not enter the separating gel. FT-IR of kafirin complexed tannins and tannin modified films showed a decrease in the absorbance at the frequency of about 1620 cm-1, suggesting a decrease in â-sheet structures. FT-IR results also suggested that the â-sheets of kafirin in dry form were probably changed into random coils during kafirin dissolution to make films. Raman spectra showed a shift in the TA peak at about 1710 cm-1 to about 1728 cm-1 in the kafirin- TA complexes, suggesting participation of the carbonyl groups of TA in TA-kafirin interaction. It is proposed that hydroxyl groups of tannin can form hydrogen bonds with carbonyl groups of random coils of kafirin during film casting. Thus, the carbonyl groups are probably not available to be reorganized into â-sheets. The other possible mode of interaction can be hydrophobic interaction between the aromatic rings of tannins and the pyrrolidine rings of proline. Because tannins have numerous aromatic rings with hydroxyl groups, it is also proposed that they can bind with more than one polypeptide chain at the same time to cross-link kafirin. This cross-linking probably produces a high Mr kafirin-tannin complex that leads to haze. The cross-linking would also lead to lower molecular mobility of modified kafirin films. This could decrease oxygen permeability, probably as a result of decreased free volume. Cross-linking could also be responsible for the increased tensile stress and decreased tensile strain of modified kafirin films. The higher tensile stress of modified• kafirin films suggests that they can have the potential to form stronger coatings around fruit such as litchi fruit to possibly reduce pericarp microcracking as an example, and thus may reduce the pericarp browning of litchi. The lower oxygen permeability of the modified films and the potential antioxidant activity of the tannins suggest that these films can be a good coating to prevent rancidity of nuts. / Thesis (PhD (Food Science))--University of Pretoria, 2006. / Food Science / unrestricted

This study used cross-sectional survey data to estimate farmers` perceptions of, and commonly cultivated ILVs, factors that influence the participation of smallholder famers in the production of Indigenous Leafy Vegetables and its contribution to household food security]. With regard to farmers` perceptions of ILVs, descriptive results reveal that a majority of the people from the study area share positive perceptions with respect to ILVs. Regression estimates for determinants of participation indicate that the production of ILVs is primarily conditioned by shared perceptions and institutional factors rather than the socio-economic attributes of farmers. Public policies that address the institutional framework (extension, credit, market and social networks) in favour of ILVs are more likely to promote production. Also, more research on the documentation and benefits of ILVs, supported by investments targeting educational campaigns towards promoting positive attitudes and dispelling fears and myths surrounding ILVs, will further promote production. With reference to the contribution of ILVs to food security, descriptive results indicate that participation in the production of ILVs leads to a higher HDDS and a lower HFIAS. Regression estimates further revealed that participation positively contributes to a higher HDDS and a lower HFIAS, suggesting that households who participate in the production of ILVs are more likely to be food secure than non-participants. Therefore, participation in the production of ILVs has significant potential to address household food security.

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Sodium phosphite was evaluated for inhibition of growth of spoilage yeasts in laboratory media and in two commercial carbonated beverages. In addition, the effects of pH and atmosphere in combination with sodium phosphite were also examined in laboratory media. Inhibition studies in laboratory media were performed with optimal or near optimal growth conditions for each yeast. Growth was monitored by measuring optical density at 600 nm. A time to significant growth was determined for experiments in laboratory media and was used to evaluate the effect that sodium phosphite and other test variables had on growth. A time to detectable growth was determined for experiments in commercial carbonated beverages and post incubation counts on observations with undetectable growth were used to evaluate the effects of sodium phosphite on yeast growth. Sodium phosphite was most effective in inhibiting growth of Zygosaccharomyces bailii, and less effective against Saccharomyces cerevisiae, and Saccharomyces uvarum respectively. Results from this investigation show the potential use of sodium phosphite as an antimicrobial food preservative has potential. / Master of Science

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O conceito de qualidade dos alimentos, na visão do consumidor, reflete a satisfação de características como sabor, aroma, aparência, embalagem e disponibilidade. Fatores econômicos e sociais como o custo e hábitos alimentares geralmente também têm influência sobre a escolha do produto. A irradiação é uma técnica eficiente na conservação dos alimentos, pois reduz as perdas naturais causadas pelos processos fisiológicos, além de eliminar ou reduzir microrganismos, parasitas e pragas, sem causar qualquer prejuízo ao alimento, tornando-os mais seguros ao consumidor; porém, pode haver aumento no custo dos alimentos. Pesquisas apontam que a praticidade é uma característica já incorporada pelo consumidor, o preço pode ser um fator de restrição à popularização do produto irradiado, embora alguns consumidores considerem que, devido ao fato de evitar desperdícios, o aumento do custo pode ser viável. O objetivo deste trabalho foi analisar o custo do uso da tecnologia de irradiação de alimentos e verificar se os consumidores, quando informados sobre as vantagens na segurança alimentar, estão dispostos a pagar por este tratamento, bem como o quanto estão dispostos a pagar. A metodologia consistiu em um estudo sobre a viabilidade econômica da implantação da tecnologia de irradiação de alimentos por meio de um levantamento sistemático da literatura especializada, com o intuito de verificar o custo de implantação e o acréscimo que o produtor terá em relação ao custo da tecnologia. Também foi realizada uma pesquisa em uma Instituição de Ensino Superior sobre a predisposição do consumidor em arcar com este custo. Os resultados do estudo indicam um acréscimo, ao produtor, que pode variar de US$ 0,01 a US$ 0,25 por quilograma e também indicam que 75% dos consumidores entrevistados aceitam pagar mais pelo alimento irradiado. A partir desses resultados, concluiu-se que quanto maior o poder aquisitivo, maior a predisposição em arcar com o acréscimo ao custo do alimento irradiado. / The concept of food quality, in the consumer point of view, reflects the satisfaction of characteristics such as flavor, aroma, appearance, packaging and availability. Economic and social factors, such as cost and eating habits, generally, also influence the choice of a product. Irradiation is an effective technique in food preservation because it reduces the losses caused by natural physiological processes, either reducing or eliminating microorganisms, parasites and pests without causing any damage to the foods and, thus, making them safer to consumers. Nevertheless, there may be an increase in the cost of foods. Research indicates that practicality is already a deep-rooted feature of consumers. The price may be a limiting factor to the popularization of the irradiated product, although some consumers consider that, due to the avoidance of waste, the increased cost may be feasible. The objective of this study was to analyze the cost of using food irradiation technology and verify (a) whether consumers, when informed of the benefits in food safety, are willing to pay for this treatment and (b) how much they are willing to pay. The methodology consisted of a study on the economic feasibility of food irradiation technology by means of a systematic survey of the literature, in order to verify the cost of this process implementation and the increase in costs for the producer. Also, a survey was conducted in an Institution of Superior Education about the consumer\'s willingness to pay for this higher price. The study results indicate a rise in costs to the producer, ranging from $ 0.01 to U.S. $ 0.25 per pound; it was also found that 75% of the consumers surveyed are willing to pay more for irradiated food. From these results it was concluded that the higher the consumption power is, the greater the willingness to afford the additional cost irradiated foods have.