Thesis (MTech (Food Technology))--Cape Technikon, 2004 / Probiotic foods are intended to supply selected viable microorganisms, for example Lactobacillus acidophilus and Bifidobacterium, to consumers. These organisms, when consumed at the daily intake of 108 , provide benefits beyond basic nutrition. Probiotic (AB) foods generally include fermented dairy products such as yoghurts and cheeses, targeted at the upmarket consumer. However, due to technical problems associated with the foods and the organism, viable Bifidobacterium rarely occur in AB foods. The principle aims of this study were to develop a suitable delivery system for Bifidobacterium to the consumer, and to supply these living organisms in the affordable traditional fermented African beverages, amasi and mahewu. This would provide the benefits of probiotics to the rural African consumer, where malnutrition and gastrointestinal diseases occur. The organism selected for this study was Bifidobacterium lactis DSM 10140, commonly associated with AB starter cultures for yoghurts. The delivery system selected was microencapsulation of B. lactis using a mixture of the generally recognised as safe (GRAS) edible gums, gellan and xanthan. Supply vehicles for the microcapsules to the consumer were amasi and mahewu. Prior to microencapsulation, rheological studies were undertaken to determine whether the gellan-xanthan gum mix would provide a suitable support matrix for microencapsulated B. lactis. This was done using a Paar Physica MGR 300 rotational rheometer with a cone plate 50-2 measuring system. Results indicated that the hydrated gellan-xanthan gum mix behaved as a non-Newtonian material, and the flow curve fitted well to the Herschel-Bulkley model. This demonstrated that the gel was a relatively viscous material with solid properties. The average yield stress of the gel was 1.515 Pa, indicating that the gel was stable, and at lower stresses would behave as a solid. The gel mix would be disrupted by shear stresses associated with mastication and peristalsis. The minimum viscosity of the gel was constant at temperatures between 46°C - 61°C. It was concluded from these data that the gel was suitable for microencapsulation and that microcapsules should only be included in soft foods, which do not require chewing. Temperatures associated with microencapsulation, at minimum gel viscosities, were not lethal to B. lactis. Bifidobacterium lactis cells were incubated under anaerobic conditions (4% H2, 10% CO2, and 86% N2) at 37°C overnight in 250 ml Tryptone-Yeast-Glucose (TYG) broth, and grown to an 00600 0.9 - 1.1. Cells were harvested and washed for microencapsulation using centrifugation. Microencapsulation of the organism was done using a mono-axial extrusion technique together with a superposed airflow, by manually extruding the aqueous gum I cell mix through a 27.5 G bevelled needle, fitted on to a 10 ml syringe. The resultant microdroplets were hardened by free fall into 0.1 M CaCI2 solution. Microcapsules were separated from the CaCI2 solution by filtration through Whatman No.1 filter paper. All procedures were carried out in a laminar flow hood. Results indicated that the method of microencapsulation used in this study was successful. Using a concentrated inoculum of B. lactis, high numbers (lOglO 11-12 etu.g-1 ) of bacteria were incorporated into the microcapsules. Therefore the daily intake would be provided by 0.1 g microcapsules. The diameter and size distribution of microcapsules were determined by laser diffractometry. This showed a maximum microcapsule diameter of 2.22 mm with 50% (w/v) of the microcapsules having a diameter of < 0.637 mm. Although this represents a considerable size variation, this would not adversely affect mouthfeel of the beverages, as only 0.1 g microcapsules would be required to obtain at least 108 B. lactis in any volume of amasi or mahewu. To enumerate immobilised viable B. lactis, two techniques were compared. These involved the use of either a pestle and mortar, or high power ultrasound (HPUS) (20 kHz, 750 W). Results showed that HPUS was superior to the pestle and mortar technique. A short exposure (15 s) to HPUS disrupted the matrix releasing all entrapped etus, whereas when using the pestle and mortar xiii technique, cells remained partially entrapped in the gel. Therefore the pestle and mortar technique yielded lower cfu values than expected. The survival of microencapsulated B. lactis, in 1 M sodium phosphate buffer, was studied as a possible means of supply of microcapsules to industry for incorporation into foods. Microcapsules were stored in the buffer for 21 days at either 4°C or 22°C. Results showed that cell viability was not significantly reduced (p>0.05) at either temperature after 21 days. Hence this form of storage could be used to deliver viable immobilised B. lactis to the food industry. In order to assess the survival of immobilised B. lactis in the GIT, the microcapsules were incubated at 37°C over a period of 240 min in simulated gastric juice (SGJ) (pH 1.5). Viable counts were performed by sampling at regular intervals. A similar study was done in simulated bile and pancreatic juices (BPJ) (pH 6.5). In SGJ, it was demonstrated that there was a significant reduction (3 log cycles) (p<0.05) of free cells after 240 min. However, this trend was not noted for microencapsulated B. lactis. Therefore, the gellanxanthan gel matrix protected B. lactis from the lethal effect of SGJ. In BPJ, no significant difference (p>0.05) was noted for surviving fractions of both immobilised and free B. lactis. Commercial pasteurised amasi (pH 4.4) and mahewu (pH 3.5) were selected as the supply vehicles for the microencapsulated B. lactis. Known numbers of viable microencapsulated and free B. lactis cells were added to both beverages. For most samples, incubation was at either 4°C or 22°C for 21 days in the presence of atmospheric oxygen. In addition, free cells were incubated anaerobically at 22°C. As oxygen is limiting in the microcapsules, these were not incubated under anaerobic conditions. The survival I shelf-life studies of commercial amasi indicated no significant difference (p>0.05) in survival rate between immobilised and free B. lactis cells. The reduction noted for viable counts of immobilised or free B. lactis cells was approximately 1.5 log cycles. Even so, after 21 days viable immobilised B. lactis (1010 0.1 g'l microcapsules) remained in excess of the daily intake 108 , whereas in the free B. lactis cells, the viable count declined to 106 mr1 . Statistical analyses showed that temperature or oxygen presence had little effect on the survival of both immobilised or free B. lactis cells (p>O.05). In mahewu, decline in viability of cells was observed for most samples. However microencapsulation enhanced cell survival at both 4°C and 22°C when compared to free cells. The decrease in viable B. lactis free cells occurred more rapidly (3 log cycles) in mahewu, than in amasi, at both 4°C and 22°C. Throughout the shelf-life studies it was apparent that viable B. lactis cell numbers did not increase. This was advantageous as metabolites associated with B. lactis growth would have adversely altered the taste of both amasi and mahewu. Sensory evaluation of the traditional fermented African beverages, enriched with either viable immobilised or free B. lactis, was done in order to determine consumer response to the product. An analytically trained 12-member taste panel analysed the beverages for colour, texture, and taste. The triangle taste test procedure was used. No differences were detected with regard to texture, and colour of the fermented beverages containing immobilised B. lactis. However, in the fermented beverages containing free cells, a change in viscosity was noted. There was a significant difference (p<O.05) recorded in flavour for both amasi and mahewu containing free B. lactis cells. In the two fermented beverages enriched with immobilised cells, significant (p<O.05) flavour differences were detected in mahewu. However, this was not observed in the amasi samples containing immobilised B. lactis. Therefore, in order to retain the sensory properties of amasi, B. lactis should be supplied in microcapsules. In mahewu, although flavour differences noted were not unpleasant to the panellists, results from this study indicate that the use of commercial flavoured mahewu should be considered as a supply vehicle for microencapsulated B. lactis. Overall, this study demonstrated that immobilisation of B. lactis in gellan-xanthan gum is possible. Microcapsules produced contained high numbers of viable B. lactis, and were suitable for incorporation into soft foods. The gel matrix significantly protected viable cells from harsh conditions associated with SGJ. Although the surviving fraction of immobilised cells, when compared to free cells, was not improved in amasi samples, it is recommended that for technological reasons associated with production of amasi, microencapsulation should be used. In mahewu, microencapsulation enhanced B. lactis survival at both 4°C and 22°C. Therefore immobilisation of B. lactis in mahewu is necessary in order to maintain the daily intake. Immobilised B. lactis should be incorporated into both beverages after fermentation, and pasteurisation.

Thesis (MTech (Food Technology))--Cape Peninsula University of Technology, 2016. / This study focused on alcoholic fermented fruit beverages that were produced from various types of fruit, value addition and thus potentially increasing the diversity of commercially available fruit wines. Non-grape alcoholic fermented fruit beverages is a complex mixture of water, alcohol, and other components, that are either initially present in the fruit, or are formed during the fermentation process. The evaluation of wine and similar fermented products quality is important for manufacturers and consumers. The routine analysis of alcoholic fermented fruit beverages acts as an important tool that is useful for wine classification, quality control and sensory evaluation. Therefore, the aims of this study were (1) to measure methanol, ethanol, titratable acidity, objective colour, total soluble solids and sensory profile as a function of yeast strain and percentage pulp in order to adapt existing technologies toward producing new fermented fruit beverage products using plums, an under-utilized agricultural produce; and (2) to measure methanol, ethanol, titratable acidity, objective colour, total soluble solids and sensory profile as a function of yeast strain, pulp percentage and sugar levels in order to adapt existing technologies toward producing new fermented fruit beverages based on red and white wine styles, while applying the technology developed in the first part of the study using red-fleshed plums, blueberries and blackberries. The independent variables (ID) were yeast strains (1) Saccharomyces cerevisiae VIN13, (2) Saccharomyces cerevisiae NT116, and (3) Saccharomyces bayanus N96, with formulations containing percentage pulp concentrations at (40%, 50% and 60%). The dependent variables (DV) constituted key quality parameters for white and red wine style, namely methanol, ethanol, titratable acidity, objective colour, total soluble solids, pH and sensory profile were measured. The optimal combination of independent variables was ascertained and in terms of the overall consumer response, for the red-fleshed plum beverage sample treatment N 96, 60% pulp showed the highest preference amongst consumers. In terms of the other dependent variables, namely methanol, ethanol, titratable acidity, objective colour, total soluble solids, pH and sensory profiles of alcoholic fermented fruit beverages based on white and red wine styles. The processing conditions developed and applied in this study towards the development of alcoholic fermented beverages utilizing plums and selected berries demonstrated ways of improving the utilization of fruit commodities by developing niche products. Hence, the development of alcoholic fermented beverages utilizing (plums and selected berries) showed potential for micro agro-industries, as well as the impact on its potential role in employment creation and income generation.

M.Tech. (Food Technology) / Coeliac disease is an autoimmune disease triggered by the ingestion of gluten; persons suffering from coeliac disease are compelled to follow a life-long gluten-free diet. Gluten-free bread, (GFB), has poor quality attributes compared to wheat bread. The effect of mageu, a traditional beverage on quality parameters of GFB with and without selected hydrocolloids was studied. Mageu produced from maize flour and commercial starter cultures were used in GFB based on sorghum, soybean flour and maize starch. It is hypothesized that mageu with or without hydrocolloids could improve GFB quality aspects. The quality parameters measured were specific volume, loaf height, bake loss, rheological attributes, crumb firmness, firming rate, onset of mould growth and sensory attributes: texture, crumb colour, crust colour, flavour and overall acceptability.....

Orientador: Fernando Broetto / Banca: Regina Marta Evangelista / Banca: Rogerio Lopes Vieites / Banca: Luciana Manoel de Oliveira / Banca: Marcelo Alvares de Oliveira / Resumo: A irradiação é uma técnica de conservação ainda pouco aceita para alimentos e bebidas no Brasil, devido a grande parte da população desconhecer seus mecanismos de ação. Dessa forma, o objetivo desse estudo foi avaliar os aspectos físico-químico, bioquímico, microbiológico e sensorial de bebida mista de extrato hidrossolúvel de soja (EHS) e suco de uva, submetida à radiação gama. Neste estudo, foram realizados quatro experimentos, visando selecionar o melhor cultivar de soja (BRS-213, BRS-258 e EMBRAPA-48) em relação às características bioativas após a aplicação de diferentes doses de radiação gama (experimento 1). No segundo experimento, selecionou-se o método mais apropriado de produção do EHS a partir de duas formas de extração; determinou-se também a dose de radiação adequada para se aplicar ao EHS (etapa 1) e ao suco de uva (etapa 2), no experimento 3. No experimento 4 foi determinada a temperatura ideal de armazenamento e a adição ou não do conservante ácido benzoico em bebida mista de EHS e suco de uva. Para o experimento 1, realizou-se análises bioquímicas, sendo que nos demais, foram realizadas análises físico-químicas, bioquímicas, microbiológicas e sensoriais. No experimento 4, realizou-se também o teste de vida de prateleira. A partir dos resultados submetidos à estatística descritiva e inferencial (testes paramétricos - t e ANOVA; e testes não paramétricos -Kruskall-Wallis e Friedmann) constatou-se que a elevação da dose de radiação gama aumentou o teor dos compostos fenólicos para os cultivares de soja BRS-213 e BRS-258, bem como a atividade da enzima superóxido dismutase no cultivar BRS-213 (experimento 1). O EHS extraído a frio apresentou maior teor de proteína, lipídios e compostos fenólicos que o EHS extraído a quente. Por outro ... / Abstract: The gamma irradiation is a conservation technique still not accepted for food and beverages in Brazil, due to much of the population ignore their mechanisms of action. Thus, the aim of this study was to evaluate the physic-chemical, biochemical, microbiological and sensory aspect of mixed beverage of soybean hydrosoluble extract and grape juice, submitted to gamma radiation. In this study, four experiments were conducted in order to select the best soybean cultivar regarding the bioactive characteristics (BRS-213, BRS 258 and EMBRAPA-48) after application of different doses of gamma radiation (experiment 1). In the second experiment, we selected the most appropriate method of producing soybean soybean hydrosoluble extract (EHS) from two forms of extraction. Also determined the adequate dosage of radiation to be applied to the EHS (step 1) and grape juice (step 2), in experiment 3. And the experiment 4 was determined the ideal storage temperature and with or without addition of the preservative benzoic acid in the mixed beverage of EHS and grape juice. For the experiment 1 was performed biochemical analyzes, and in the other were conducted in physical-chemical, biochemical, microbiological and sensory analiyses. In experiment 4, it was also carried shelf life test. When results submitted to descriptive and inferential statistics (tests parametric- t and ANOVA, and nonparametric tests -Kruskall-Wallis and Friedman) it was found that the elevation of gamma radiation dose increased the content of phenolic compounds for the soybean cultivars BRS-213 and BRS-258 and SOD activity in cultivar BRS-213 (experiment 1). The EHS cold extraction has a higher protein, lipid and phenolic compounds content that the EHS hot extraction. On the other hand, the second extraction showed better results in sensory analysis (experiment 2). In experiment 3 EHS (step 1) submitted to 8 kGy showed lower protein and phenolic ... / Doutor

Thesis (Ph.D.(Microbiology)) -- University of Limpopo, 2022 / Traditional sorghum juice is produced in many African countries for human consumption. The juice is very rich in calories, B-group vitamins including thiamine, folic acid, riboflavin, nicotinic acid, and essential amino acids such as lysine. Low earning income women at village level produce sorghum juice for home consumption and sale. The short shelf life (2 to 3 days) of sorghum juice is a major problem for both the brewers and consumers of this drink. The aim of the study was to use 12 Combretum plants to improve the microbiological quality and shelf life of sorghum juice. Fresh stems and leaves of C. caffrum, C. vendae, C. erythrophyllum, C. elaegnoides, C. apiculatum, C. imberbe, C. adenogdium, C. padoides, C. bracteosum, C. kraussii, C. mkuzense and C. zeyherii were collected at Nelspruit, National Botanical Gardens, Mpumalanga, South Africa. Voucher specimens and tree labels were used to verify the identity of the plants. The stems and bark collected were cut into pieces and air dried for 30 days. When dried, the plant material was ground to a fine powder and stored in paper bags at room temperature. The wood was burnt in an open fire; fuel was not used to minimise contamination. The qualitative phytochemical composition of both the leaves and stems of Combretum plants analysed in this study revealed the presence of saponins, tannins, terpenoids, steroids, cardiac glycosides and flavonoids. The following phytoconstituents were lost in the ashes; tannins with the exception of C. mkuzense and C. padoides; cardiac glycosides and flavonoids. The quantitative phytochemical analyses revealed that both the leaves, stems and some ashes such as C. apiculatum and C. vendae contained appreciable levels of phenolic compounds, tannins and flavonoids. Quantitative analysis of antioxidant activity, the 2, 2, diphenyl-1-picrylhydrazyl (DPPH) assay was used as a screen test for the radical scavenging ability of the compounds present in the different 36 70% acetone extracts. DPPH screening method indicated great scavenging activity with the 70% acetone leaf extracts of C. kraussii, C. zeyherii and C. mkuzense. The leaf and stem extracts showed substantial great antioxidant activity in a concentration-dependent manner. There was a significant decrease in the antioxidant activity in the ashes (p=001), when compared to both the leaves and the stems. The proximate and nutritional analysis of the 70% acetone extracts were performed by AOAC and ICPE protocols, respectively. The results indicated that all the extracts had substantial amounts of ash, moisture, protein and energy. Mineral content of the plant parts was analysed as well, calcium had the highest concentration, while zinc was lowest in concentration. The mineral content decreased significantly in the stems (p ≤ 0.05) when compared to the leaves. There was a further decrease in mineral content with regard to the ashes with the exception of calcium. Based on these findings, the leaves and ashes of C. adenogonium and C. apiculatum could provide a good source of calcium in the diet, while C. adenogonium, C. bracteosum and C. apiculatum had high levels of sodium. A serial micro-dilution assay was used to determine the minimum inhibitory concentration (MIC) values for 70% plant extracts using tetrazolium violet reduction as an indicator of growth. Two Gram-positive (Stapylococcus aureus ATCC 29213 and Enterobacter faecalis ATCC 29212) and two Gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) bacterial strains were used in this study. The leaves had good antibacterial properties with the lowest MIC value being 0.04 mg/ml against E. coli and S. aureus. E. faecalis was found to be resistant against all the leaves with the exception of C. imberbe. The stem extracts of Combretum spp. tested in the study showed antimicrobial properties with the lowest MIC value being 0.04 mg/ml against E. coli shown by C. bracteosum. However, E. faecalis was resistant against all the 12 plants tested. All the test microorganisms showed resistance to the ashes, with the exception of S. aureus, which was found to be susceptible to 75% of the test ash extracts with the lowest MIC value of 0.16 mg/ml. Cytotoxicity and anticancer activity of the acetone extracts of the 12 Combretum plants were evaluated using tetrazolium-based colorimetric assay (MTT assay) on A549 lung carcinoma cells. The assays revealed that 50% of the leaf extracts of tested plants showed cytotoxicity and cell proliferation inhibition in A549 lung carcinoma cells in a concentration-dependent manner. The A549 cells were more sensitive to the following plants: C. elaegnoides, C. erythrophyllum C. imberbe, C. kraussii and C. mkuzense. The following stems extract, C. adenogdium and C. caffrum did not have any anticancer activity, whereas C. apiculatum and C. bracteosum were only able to reduce cell viability to less than 60%. C. mkuzense, C. padoides, C. vendae and C. zeyherii acted in a concentration-depended manner with the greatest activity seen at the highest concentration (1000 µg/ml). The plants had activity at concentrations between 31.25 and 1000 µg/ml allowing only 20% and 50%, respectively, of the cells to remain viable. Ashes from C. mkuzense showed good anti-cancer activity at the highest concentration (1000 µg/ml) reducing cell viability to around 10%. Enterobacteriaceae, total coliform, S. aureus, B. cereus, E. coli and lactic acid bacteria viability were studied during the four weeks storage period of prepared sorghum juices. Juice samples were collected after preparation; the samples were serially diluted using peptone water. Tempo instrument (Biomereiux) was used to enumerate total coliform, total aerobic count, E. coli, S. aureus, lactic acid bacteria, enteric bacteria, yeast and mould using the most probable number following the manufacturers instruction. C. mkuzense and C. padoides plants were able to inhibit the growth of B. cereus, lactic acid bacteria and S. aureus during the first three weeks of storage. E. coli was not present throughout the four weeks storage time. Vitek 2 Compact (Biomereiux) was used for the characterisation and identification of the dominant bacterial isolates using biochemical reactions. The isolates were characterised by morphological differences. Sixty five percent of the isolates were the Enterobacter genus that are commonly found in soil, water, and sewage. The nutritional composition and sensory properties of the prepared sorghum juices treated with Combretum plants were investigated. All the juices had appreciable amounts of protein, ash and energy. Sorghum juice treated with ashes of C. caffrum, C. erythrophyllum and C. kraussii had the highest levels of proteins when compared with other treated sorghum juices. The sorghum juices prepared in the study had varying levels of trace element or minerals with potassium -(3, 55 – 104 mg/l) and calcium (3.2-148 mg/l). Similarly, cobalt (-1.22), coppr (-0.99), iron(-0.962), magnesium (0.004), sodium (-0.145), nickel (-2.7)) and zinc (-1.2)are present in very low amounts. The juices treated with ashes had relatively higher levels of calcium, potassium, magnesium and sodium. Sorghum juices treated with the ashes had better sensory and organoleptic properties when compared with those treated with the leaves. The juices treated with the ashes of C. caffrum and C. bracteseum were more accepted by most of the panellist when compared with other treated juices. Overall, this study presents valuable information on the phytochemical composition, nutritional composition and antioxidant properties of some Combretum species in South Africa. It recommended its use as food and in pharmaceutical preparations for the local industries. In addition, Combretum plants showing the effects tested in this study may be explored further for development into drugs. functional food as food preservatives and nutraceutical applications, beside their traditional use / University of Limpopo and Foodbev SETA

Thesis (PhDAgric (Viticulture and Oenology. Wine Biotechnology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Stuck alcoholic fermentations are a major enological problem for the international winemaking industry. Incomplete wine fermentations are frequently characterized by high residual fructose concentrations and the near-absence of residual glucose, a fact that is due to the glucophilic character of the wine yeast Saccharomyces cerevisiae. Wines with high contents of post fermentation sugar are very susceptible for microbial spoilage since residual fructose and/or glucose can be metabolized by bacteria and yeast to undesired by-products such as volatile acid and off-flavours, resulting in wine spoilage and considerable economic losses. It has been reported that stuck fermentations are usually caused by several synergistically acting inhibition factors, and the glucose to fructose ratio (GFR) is thought to play an important role in this context. This study is aimed at contributing towards a better understanding of this industrial problem, and at finding industrially applicable solutions. In a first part, this study describes the isolation of two appropriate strains of the fructophilic yeast Zygosaccharomyces bailii from the natural microflora of grapevine, followed by trials in small scale test fermentations using stuck industrial fermentations as model media. These experiments were expanded to also investigate large scale industrial fermentations. As a result, a strategy for the treatment of stuck fermentations was developed and successfully applied in several wineries with fermentation problems. This methodology represents an entirely novel and industrially applicable solution to high residual fructose levels. In a second part, the data contributes to elucidating the molecular nature of the fructophilic phenotype of Z. bailii by characterizing some of the genes and proteins that may be responsible for the fructophilic character. In particular, the investigation focused on the first two steps of hexose metabolism, the transport of sugar into the cell by permeases and sugar phosphorylation by hexokinases, which combined are thought to be primarily responsible for sugar preference. One result of this study was Fructoferm W3©, a dry yeast product which is commercially available. Fructoferm W3 was awarded with the innovation medal for enological products at Intervitis/Interfructa, Stuttgart, Germany in 2007. / AFRIKAANSE OPSOMMING: Die voorkoms van steek alkoholiese fermentasies is ‘n ernstige problem in die internasionale wyn industrie. Onvolledige fermentasies word dikwels gekenmerk deur hoë residuele fruktose konsentrasies en die veitlike afwesigheid van residuele glukose. Die kenmerke kan meestal toegeskryf word aan die glukofilliese kakakter van die wyngis Saccharomyces cerevisiae. Wyne met ‘n hoë suiker inhoud na die afloop van fermentasie is vatbaar vir mikrobiese bederf aangesien residuele fruktose en/of glukose gemetaboliseer kan word deur bakterië en gis om ongewenste byprodukte soos vlugtige sure en bygeure te vorm wat kan lei tot wyn bederf en aansienlike ekonomies verlies. Dit is vasgestel dat steek fermentasies gewoonlik veroorsaak word deur verskeie sinergisties werkende inhibisie faktore, waartoe die glukose/fruktose verhouding ‘n noemenswaardiege bydrae lewer. Die mikpunt van hierdie studie was om ‘n bydrae te lewer tot die begrip van steek fermentasies en die daarstelling van moontlike industriële oplossings. Die eerste deel van die werk beskryf die isolasie van twee rasse van die gis Zygosaccharomyces baillie uit die natuurlike wingerd mikroflora, gevolg deur steekproewe in die vorm van kelinskaalse fermentasies met steek industriële fermentasies gebruik as model media. Hierdie ekserimente is vervolgens uitgebrei om grootskaalse industriële steek fermentasies te bestudeer. Die uitkoms van hierdie werk het gelei tot die ontwikkeling van ‘n strategie vir die behandeling van steek fermentasies wat susksesvol toegepas is in verskeie wynmakerye. Die metodiek bring ‘n nuwe en industrieel toepasbare oplossing vir hoë residuele fruktose vlakke. Die data aangebied in die tweede afdeling dra by tot die verheldering van die molekulêre natuur van die fruktofilliese fenotipe van Z. baillie deur die tipering van gene en protiëne wat moontlik verantwoordelik is vir die fruktofilliese karakter van die gis. Die ondersoek het spesifiek op die eerste twee stappe van heksose metabolisme, naamlik die invoer van suiker in die sel deur permeases en suiker fosforilering deur heksokinases, gekonsentreer. Die kombinasie van die twee prosesse is vermoedelik verantwoordelik vir die regulering van suiker voorkeur. ‘n Gevolg van die studie was die ontwikkeling van ‘n droë gisproduk, Fructferm W3©, wat kommersieel beskikbaar gestel is. Fructoferm W3 is in 2007 toegeken met die innovasie medalje vir wynkundige produkte by Intervittis/Interfructa in Stuttgart, Duitsland.

D. Tech. Food Technology. / Discusses a range of lactobacilli and bifidobacteria were isolated from functional food products and pharmaceutical preparations and also obtained from culture collections. They were then subjected to phylogenetic analysis for accurate identification and classification and the probiotic properties of the organisms was evaluated. The isolates were then screened for inhibitory activity against a range of pathogenic bacteria and Candida albicans strains. Selected isolates that were found to have the necessary inhibitory and probiotic properties were recommended for inclusion in an envisaged synbiotic, maize-based beverage that would, in a subsequent study, be subjected to a nutritional intervention trial aimed at alleviating oral thrush in human patients. The specific objectives: to investigate and illustrate the superiority of rpoA and pheS gene sequencing compared to 16S rRNA gene sequencing in the identification and phylogenic assignment of Lactobacillus isolates ; to determine the precision of selected protein-coding gene sequencing in comparison with 16S rRNA gene sequencing for the discrimination and phylogenetic analysis of Bifidobacterium isolates ; to investigate the probiotic properties of selected bacterial strains in terms of antibacterial activity, anti-Candida activity, acid resistance, bile tolerance and antibiotic resistance ; to determine the potential of Lactobacillus isolates to inhibit the growth of each of seven Candida albicans strains in fermented maize gruel and to establish the factors contributing to Candida inhibition and to determine the antimicrobial and antioxidant activity of intracellular extracts and to elucidate compounds in methanol extracts from selected Lactobacillus strains.

Thesis (MSc Food Sc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT:Aspalafhus linearis is an indigenous fynbos plant cultivated in the Clanwilliam area of the Western Cape, South Africa. The rooibos tea that is prepared from this plant, has become popular worldwide mainly due to the alleged health properties. Studies on the anti-microbial properties of green, black and oolong teas have shown that these teas have strong anti-microbial activity against a wide range of microbes. No studies have been done on the anti-microbial activity of rooibos tea and the aim of this study was to determine what impact rooibos tea extracts would have on the growth of different food spoilage and potential pathogenic microbes. Water and ethyl acetate extracts of fermented and unfermented rooibos tea were used to determine the inhibitory effect on the growth of an Escherichia coli strain. The E. coli culture was grown in tea-MRS with either added fermented or unfermented rooibos tea extracts. Both the water and ethyl acetate extracts showed a strong inhibitory effect against the E. coli strain in that there was a decrease in the final bacterial cell density (Nmax)(from 0.59 00 to 0.25 00) and the maximum specific growth rate (~max)(from 1.12 h-1 to 0.20 h-1) and an increase in the doubling time (~) (from 0.59 h to 1.80 h) and lag time (tlag)(from 4.81 h to 6.60 h) as the concentration of the soluble solids of the tea extracts was increased from 0.5 to 5.0 g.r1 . Furthermore, it was found that the fermented rooibos tea had a much stronger inhibitory effect (69% decrease in growth at 5.0 g.r1 soluble solids) compared to the unfermented rooibos tea extracts (35.1% decrease in growth at 5.0 g.r1 soluble solids). The resulting data indicated that rooibos tea had a very strong inhibitory effect on the growth of the E. coli strain. It was also found that the water extracts of rooibos tea showed a stronger inhibitory effect on the growth of the E. coli than the ethyl acetate extracts, indicating that the antimicrobial activity of rooibos tea is not exclusively due to the polyphenolic content - individual compounds. It was also determined that the rooibos tea water extracts showed a bacteriostatic action against the E. coli strain in that as soon as the tea is no longer part of the growth medium, the E. coli resumed a normal growth pattern. The data obtained showed that the inhibitory effect of rooibos tea water extracts (69% decrease in growth) against the growth of E. coli was more pronounced than that found when black tea water extracts (25.7% decrease in growth) at the same concentrations were used.Rooibos tea water extracts (0.5 - 5.0 g.r1) of fermented and unfermented tea were also used to determine the inhibitory effect on other food spoilage microbes and potential pathogens. Strains of Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces cerevisiae and Zygosaccharomyces rouxii were grown in the presence of fermented and unfermented rooibos tea water extracts. The effect that fermented rooibos tea had on the growth of all the microbes tested was in the following order: Staph. aureus (90.8% decrease in growth) > L. monocytogenes (89.2% decrease in growth) > Strep. mutans (84.1% decrease in growth) > B. cereus (80.3% decrease in growth) > Sacch. cerevisiae (77.7% decrease in growth) > E. coli (69.0% decrease in growth). The rooibos tea clearly had an inhibitory effect on the growth of all the microbes, with the exception of the Z. rouxii strain where the presence of the tea water extracts was found to enhance the growth. The inhibitory effect of rooibos tea on the growth of these microbes was shown by changes in the growth parameters with Nmax and IJmaxshowing decreases, while the ld and tlagincreased as the concentration of the tea soluble solids was increased. As with E. coli, the fermented rooibos tea water extracts showed the stronger inhibitory effect on the growth of the various microbes. The data obtained in this study suggests that rooibos tea is not effective as an anti-microbial agent against all yeast species, but will strongly retard the growth of specific Gram-positive and Gram-negative bacteria. As long as rooibos tea is present, strong anti-microbial activity will be observed at a cup of tea concentration of 2.5 g.r1 soluble solids. These results may be of value to support the health claims associated with rooibos tea and may in the future lead to the use of rooibos tea as a "natural" food preservative. / AFRIKAANSE OPSOMMING:Aspalathus linearis is 'n inheemse fynbosplant wat gekultiveer word in die Clanwilliam area van die Wes Kaap, Suid-Afrika. Rooibostee, wat gemaak word van hierdie plante, het baie gewild geword wereldwyd a.g.v. die gesondheidsaspekte van hierdie tee. Studies toon dat groen, swart en oolong tee sterk anti-mikrobiese aktiwiteit het teen 'n wye reeks mikrobes. Aangesien daar voorheen geen studies gedoen is op die anti-mikrobiese aktiwiteit van rooibostee nie, was die doel van hierdie studie om die effek van rooibostee te bepaal op die groei van verskillende voedselbederwers en potensiele patogeniese mikrobes. Water- en etielasetaat-ekstrakte van gefermenteerde en ongefermenteerde rooibos tee is gebruik om die inhiberende effek op die groei van Escherichia coli te bepaal. Escherichia coli is gegroei in tee-MRS met bygevoegde gefermenteerde of ongefermenteerde rooibostee-ekstrakte. Seide die water- en etielasetaatekstrakte van rooibostee het 'n sterk inhiberende effek gewys teen E. coli en dit word gestaaf deur 'n afname in die finale bakteriese seldigtheid (Nmax)(vanaf 0.59 00 tot 0.25 00) en die maksimum spesifieke groeitempo (lJmax) (vanaf 1.12 h-1 tot 0.20 h-1) en 'n toename in die verdubbelingstyd (~) (vanaf 0.59 h tot 1.80 h) en die sloerfase (tlag)(vanaf 4.81 h tot 6.60 h) 5005 wat die konsentrasie van oplosbare vastestowwe van die tee toeneem van 0.5 tot 5.0 g.r1 . Verder is daar gevind dat die gefermenteerde rooibostee 'n baie sterker inhiberende effek het (69% afname in groei by 5.0 g.r1 oplosbare vastestowwe) in vergelyking met die ongefermenteerde rooibostee-ekstrakte (35.1% afname in groei by 5.0 g.r1 oplosbare vastestowwe). Die resultate van die data dui aan dat rooibos tee 'n baie sterk inhiberende effek het op die groei van die E. coli spesie. Die waterekstrakte van rooibostee het 'n sterker inhibisie getoon teen die groei van E. coli as die etielasetaat-ekstrakte, wat aandui dat die anti-mikrobiese aktiwiteit van rooibostee nie eksklusief toegeskryf kan word aan die polifenoliese samestelling nie. Daar is ook gevind dat rooibostee water-ekstrakte 'n bakteriostatiese effek het teen E. coli, want sodra die tee ekstrakte nie meer teenwoordig is in die groeimedium nie, hervat E. coli normale groei. Die data wys ook dat die inhiberende effek van rooibostee water-ekstrakte (69.0% afname in goei) teen E. coli baie sterker is as die van swart tee water-ekstrakte (25.7% afname in groei) by dieselfde konsentrasies.Rooibostee water-ekstrakte (0.5 - 5.0 g.r1) van gefermenteerde en ongefermenteerde rooibostee is ook gebruik om die inhiberende effek te bepaal teen ander voedselbederwers en potensiele patogene. Spesies van Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Streptococcus mutans, Saccharomyces cerevisiae en Zygosaccharomyces rouxii is gegroei in die teenwoordigheid van gefermenteerde en ongefermenteerde rooibostee waterekstrakte. Die effek wat gefermenteerde rooibostee het op die groei van die getoetste mikrobes is 5005 volg: Staph. aureus (90.8% afname in groei) > L. monocytogenes (89.2% afname in groei) > Strep. mutans (84.1% afname in groei) > B. cereus (80.3% afname in groei) > Sacch. cerevisiae (77.7% afname in groei) > E. coli (69.0% afname in groei). Rooibostee het 'n duidelike inhiberende effek gehad teen al die organismes, behalwe teen Z. rouxii spes ie, waar die teenwoordigheid van rooibostee die groei van die organisme bevorder het. Die inhiberende effek van rooibostee teen die groei van hierdie mikrobes word ondersteun deur die groei parameters waar die Nmaxen IJmaxafgeneem het terwyl die ~ en tlagtoegeneem het 5005 wat die konsentrasie van die oplosbare vastestowwe toeneem. Die gefermenteerde rooibostee water-ekstrakte het ook 'n sterker inhiberende effek op die groei van die verskillende mikrobes net 5005 met E. coli. Die data wat verkry is van hierdie studie dui aan dat rooibostee nie effektief sal wees as 'n anti-mikrobiese middel teen aile gis spesies nie, maar dit sal die groei van spesifieke Gram-positiewe en Gram-negatiewe bakterie sterk vertraag. So lank as wat rooibostee teenwoordig is, sal sterk anti-mikrobiese aktiwiteit waargeneem word by 'n koppie-tee konsentrasie van 2.5 g.r1 oplosbare vastestowwe. Hierdie resultate kan help om die gesondheidseienskappe geassosieer met rooibostee te ondersteun en help om die gebruik van rooibostee as 'n "natuurlike" preserveermiddel te bevorder. dedicated to my parents