Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2006. / Kefir is a traditional fermented milk that is carbonated, has a sharp acidic taste, yeasty flavour and contains a low percentage alcohol (less than 2% (v/v)). The beverage is manufactured by fermenting milk with Kefir grains, comprised of microorganisms, polysaccharides and milk proteins. The microbial population of Kefir grains primarily include lactic acid bacteria (LAB), namely lactococci and lactobacilli, yeasts, Acetobacter and filamentous fungi. Kefir exhibits antimicrobial activity in vitro against some fungi, and Grampositive and Gram-negative bacteria. Although the exact cause of this inhibition in Kefir is not known, the ability of LAB to inhibit the growth of closely related bacteria is well known. This inhibition of pathogenic and spoilage microbes may be due to the production of organic acids, hydrogen peroxide, acetaldehyde, diacetyl, carbon dioxide or bacteriocins. Acid is not the only contributor to the antimicrobial activity of Kefir and Kefir grains, and bacteriocins may play a role in the inhibitory activity. The bacteriocin producer Lactobacillus plantarum ST8KF, isolated from Kefir and Kefir grains, produces a bacteriocin 3.5 kDa in size. The mode of activity of bacteriocin ST8KF (bacST8KF) is thought to be bacteriostatic in exponential cultures of Enterococcus faecalis E88, Lactobacillus casei LHS, Lactobacillus curvatus DF38, Lactobacillus sakei DSM 20017, Lactobacillus salivarius 241 and Listeria innocua F and LMG 13568. The peptide is sensitive to proteolytic enzymes and does not adsorb to the surface of the producer cell. The bacteriocin is stable between pH 2.0 and 10.0, and for 20 min at 121°C. Maximum bacteriocin activity was observed in modified MRS medium supplemented with glucose or saccharose, meat extract, KH2PO4, glycerol, thiamine or cyanocobalamin, or in modified MRS medium without tri-ammonium citrate. Maximum levels of adsorption of bacST8KF (80%) to Lb. casei LHS and Lb. sakei DSM 20017 were recorded. Adsorption (80%) of the bacteriocin to Lactobacillus paraplantarum ATCC 700211T and Streptococcus caprinus ATCC 700066, which are not sensitive to the bacteriocin was also recorded. Optimal adsorption to E. faecalis E88 was recorded at 25°C at pH 2.0, and to L. innocua LMG 13568 at 4°C, 10°C and 25°C at pH 6.0. Potassium ions, MgCl2, Tris, NH4- citrate, Na-acetate, Na2CO3, EDTA and SDS led to decreased adsorption to both sensitive strains, while NaCl and mercaptoethanol resulted decreased adsorption to E. faecalis E88, but not to L. innocua LMG 13568. Methanol resulted in lower levels of adsorption to L. innocua LMG 13568 but not to E. faecalis E88. Triton X-100 and Triton X-114 increased the adsorption of bacST8KF by 40%, and ethanol and chloroform had no effect on bacteriocin adsorption. The growth of Lb. plantarum ST8KF and L. innocua LMG 13568 in a mixed culture resulted in an increase of bacST8KF production. Cells treated with bacST8KF secreted DNA and galactosidase. As bacST8KF remains stable under a variety of conditions, the bacteriocin may have application, if awarded GRAS (generally regarded as safe) status, in various food products as a natural additive or preservative. The genes encoding bacteriocin production are located on a 3.9 kilo base (kb) plasmid. Curing of the plasmid resulted in a mutant strain of Lb. plantarum ST8KF, and the Lb. plantarum strains ST8KF(+) and ST8KF(-) differed with regards to antibiotic resistance and carbohydrate fermentation reactions. The wild type and the cured strain were incorporated into Kefir grains during mass cultivation. The survival of the bacST8KF sensitive Enterococcus mundtii ST4SA added to the milk during Kefir production using the enriched mass cultured grains was monitored using fluorescent in situ hybridization. Enterococcus mundtii ST4SA was present in higher numbers in the ST8KF(-) Kefir system when compared to the ST8KF(+) system. It can, therefore, be concluded that Lb. plantarum ST8KF(+) contributes to the antimicrobial activity of Kefir through the production of bacteriocin ST8KF.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2008. / South Africa as well as other grain producing and exporting countries’ grading systems strongly relies on hectolitre mass (HLM) as a guide to grain quality. It is known that these countries use either one of two types of HLM equipment. These devices consist of either a funnel or a cylindrical device (chondrometer) with a measuring cylinder of known volume underneath which is then filled with grain in a controlled manner. Subsequently the HLM devices from Australia, Canada, France, Germany, South Africa, the United Kingdom (UK) and the United States of America (USA) were compared using impurity free mixed wheat, single South African cultivars as well as maize samples. Very little variation in HLM measurements within the HLM devices was observed with intra-class correlation (ICC) agreement values close to one. Comparing the actual HLM values obtained with the respective devices showed that the results obtained with the Australian device was significantly (P < 0.05) higher, and those obtained with the South African devices significantly (P < 0.05) lower compared to the other devices. As would be expected the devices showed better overall ICC agreement when the HLM tests were performed with the single cultivar samples (ICC agreement = 0.762) as opposed to the mixed wheat samples (ICC agreement = 0.523). However, the HLM values obtained with all the devices correlated well with each other (ICC consistency >0.90) indicating that correction factors can therefore be developed to convert the HLM results between devices. When ten South African devices were compared statistical differences were observed, but the overall ICC agreement (0.975) and consistency (0.993) values indicated that the differences would not be significant in practice. Hectolitre mass determinations performed on samples prior to and after impurities have been removed revealed that the removal of impurities resulted in a significant (P < 0.05) increase in HLM. The effect of operator was shown to be significant (P < 0.05) when operators with three levels of competency, i.e. skilled, semi-skilled and unskilled, were investigated. The effect of wet and dry cycles on the HLM measurements was investigated and the results showed that wetting and drying could change the integrity of the wheat. Moisture correction factors cannot be applied to convert the HLM values of grain that underwent moisture changes as different samples responded differently to the moisture treatments. Comparing the respective devices with mixed maize samples (impurities not removed) very little variation in HLM measurements within each device was observed. The comparison of the devices revealed that the HLM measurements obtained with the Australian and French devices were significantly (P < 0.05) higher and that obtained from the Canadian device significantly (P < 0.05) lower compared to those obtained with the other devices. Again it was shown that the devices correlate well (ICC consistency > 0.97) and that correction factors can be applied to convert HLM results between devices. An alternative to the use of correction factors could be the replacement of the South African device with the German device for both wheat and maize. The removal of impurities from the maize samples significantly (P < 0.05) increased the HLM values. Therefore, it is likely that correction factors can be used to convert HLM values of maize samples before and after removal of impurities.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The consumption of herbal teas is an increasing phenomenon among tea consumers globally. However, herbal teas that are not pre-treated to reduce their microbial load are a health risk to consumers, in spite of their potential health-promoting properties. The aim of this study was to develop a steam pasteurisation treatment to reduce the microbial load on Lippia multiflora Moldenke (Verbanaceae) tea leaves, a herbal tea from Ghana, identify the bacteria present, and to evaluate the effect of the steam treatment on the bioactive constituent of the leaves. An HPLC method was developed and optimised for the identification and quantification of verbascoside, the major antioxidant compound of L. multiflora herbal infusion. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was used to confirm the presence of the compound in the infusion. Ascorbic acid was used as a stabilising agent during the quantification process to prevent the degradation of verbascoside. The hot water infusion of L. multiflora was compared to those of Aspalathus linearis (rooibos) and Cyclopia spp. (honeybush) on the basis of their soluble solids and total polyphenol contents, as well as on their antioxidant activities. In addition to verbascoside, another compound with the same parent and fragment ions as verbascoside was present in the infusion. A 100 ml infusion of L. multiflora had significantly (P < 0.05) higher soluble solids and total polyphenol contents, and antioxidant activities than those of rooibos and honeybush. The rooibos infusion showed significantly (P < 0.05) higher soluble solids and total polyphenol contents as well as antioxidant activities than honeybush. On the basis of soluble solids, rooibos showed a significantly (P < 0.05) higher total polyphenol content and a lower ferric-reducing activity than L. multiflora. Both teas, however, did not differ significantly with respect to the DPPH antioxidant activity. The effect of steam pasteurisation on the microbial load of L. multiflora herbal tea leaves was evaluated. Five samples of the tea were steam pasteurised at 99.8°C for 2.5 min and five samples were unpasteurised. Microbial enumeration was conducted in duplicate on potato dextrose agar (PDA), plate count agar (PCA), violet red bile agar (VRBA), yeast peptone dextrose agar (YPDA), and de Man Rogosa Sharpe agar (MRS). Morphologically distinct colonies were isolated, sub-cultured and their Gram reaction recorded. These bacteria were identified to the species level using 16S ribosomal DNA (rDNA) sequence data. Most of the bacteria identified belonged to the genus Bacillus. One species each from the genera Pantoea and Kocuria were also identified, but only the Bacillus species survived the steam treatment. Coliform bacteria detected prior to pasteurisation were not detected after steam treatment. Steam pasteurisation reduced the microbial load from 104 to 102 cfu.g-1. The effects of the steam pasteurisation on the soluble solid, total polyphenol, and the active compound contents of L. multiflora, as well as the antioxidant activities were studied. Pasteurisation did not significantly (P > 0.05) change the soluble solids, total polyphenol and active compound contents, or the antioxidant activity. Steam pasteurisation is potentially an effective method to treat L. multiflora herbal teas prior to consumption. However, the steam treatment should complement good agricultural and hygienic practices rather than replace them as some bacteria can survive this treatment. The identification and quantification of verbascoside in L. multiflora infusion, as well as the relatively higher antioxidant contents compared to rooibos and honeybush should provide the basis for future studies on the therapeutic application of this herbal tea. Also, verbascoside could potentially form the basis for future quality control of L. multiflora. / AFRIKAANSE OPSOMMING: Daar is 'n wêreldwye toename in die verbruik van kruietee. Kruietee wat egter nie vooraf-behandelings ontvang om die mikrobiese lading te verlaag nie kan, ten spyte van moontlike gesondheidsvoordele, ook 'n potensiële gesondheidsrisiko vir verbruikers inhou. Die doel van hierdie studie was om 'n stoompasteurisasie-behandeling te ontwikkel wat die mikrobiese lading op Lippia multiflora teeblare, 'n kruietee van Ghana, te verlaag. Verder is die teenwoordige bakterieë geïdentifiseer en die effek van 'n stoombehandeling op die bio-aktiewe komponente in die teeblare is ook geëvalueer. 'n Hoë-druk vloeistof-chromatografie metode is ontwikkel en ge-optimiseer vir die identifikasie en kwantifisering van verbaskosied, 'n hoof antioksidant komponent in L. multiflora kruie aftreksels. Vloeistof chromatografie, gekoppel aan in-lyn massa spektroskopie is ook gebruik om die teenwoordigheid van die komponent in die aftreksel te bevestig. Tydens die kwantifiseringsproses is askorbiensuur as 'n stabiliseringsagent gebruik om die degradasie van verbaskosied te voorkom. Die warm water aftreksel van L. multiflora is vergelyk met die van Aspalathus linearis (rooibos) en Cyclopia spp. (heuningbos) in terme van hul opgeloste vastestof- en totale polifenol inhoude, asook hul antioksidant aktiwiteite. 'n Ander komponent buiten verbaskosied, maar met dieselfde ouer en fragment ione, was ook in die aftreksel teenwoordig. 'n 100 ml L. multiflora aftreksel het beduidend (P < 0.05) meer opgeloste vastestowwe, totale polifenole en antioksidant aktiwiteit getoon as rooibos en heuningbos. Rooibos het weer beduidend (P < 0.05) meer opgeloste vastestowwe, totale polifenole, en antioksidant aktiwiteit as heuningbos. In terme van opgeloste vastestowwe het rooibos 'n beduidende (P < 0.05) hoër totale polifenol inhoud en laer ferriet-reduserende aktiwiteit as L. multiflora. Beide tee het egter nie beduidend verskil ten opsigte van hul antioksidant aktiwiteit nie. Die effek van stoompasteurisasie op die mikrobiese lading van L. multiflora kruieteeblare is geëvalueer. Vyf teemonsters is gestoompasteuriseer by 99.8°C vir 2.5 min en 5 verdere monsters is nie gepasteuriseer nie. Mikrobe-tellings is in Mikrobe-tellings is in v duplikaat op potato dextrose agar (PDA), plate count agar (PCA), violet red bile agar (VRBA), yeast peptone dextrose agar (YPDA), en de Man Rogosa Sharpe agar (MRS) gedoen. Morfologies onderskeibare kolonies is geïsoleer, her-gekweek en hul Gram status genotuleer. Hierdie bakterieë is daarna tot op spesie-vlak geïdentifiseer deur 16S ribosomale DNS (rDNS) volgorde bepalings. Die meerderheid van die geïdentifiseerde bakterieë behoort tot die genus Bacillus en een spesie elk van die genera Pantoea en Kocuria is ook geïdentifiseer. Slegs Bacillus spesies het egter die stoompasteurisasie behandeling oorleef. Kolivorme bakterieë wat voor pasteurisasie waargeneem is was afwesig na die stoom behandeling. Stoompasteurisasie het ook die mikrobiese lading van 104 na 102 kve.g-1 verminder. Die effek van stoompasteurisasie op die opgeloste vastestowwe, totale polifenole en die aktiewe-komponent inhoud van L. multiflora, asook die antioksidant aktiwiteit is bestudeer. Pasteurisasie het die opgeloste vastestowwe, totale polifenole, aktiewe komponente en die antioksidant aktiwiteit nie-beduidend (P > 0.05) verander. Stoompasteurisasie kan potensieël 'n effektiewe metode wees vir die behandeling van L. multiflora kruietee voor verbruik. Die stoombehandeling moet egter saam met goeie landbou- en higiëniese praktyke gebruik word eerder as om dit te vervang aangesien sommige bakterieë hierdie stoombehandeling kan oorleef. Die identifikasie en kwantifisering van verbaskosied in L. multiflora aftreksels, asook die hoër antioksidant inhoud vergeleke met rooibos en heuningbos verskaf moontlikhede vir verder navorsing in die terapeutiese aanwending van hierdie kruietee. Verbaskosied kan ook moontlik die basis vorm vir toekomstige kwaliteitskontrole van L. multiflora.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / Endoxylanases are known to improve dough stability, oven spring, loaf volume, crumb structure and shelf life. The use of endoglucanases (cellulases) usually results in increased bread loaf volume, bread score and reduced crumb firmness. Even though bakeries use ‘pure’ enzymes in their formulations, they are supplied with an enzyme mixture which can contain up to five different enzymes. These mixtures often also include an emulsifier and ascorbic acid. To compare the ability of endoxylanase and endoglucanase to improve bread quality characteristics, a commercial endoxylanase (from Aspergillus niger) and endoglucanase (from Trichoderma reseei) were evaluated together with a pure endoxylanase and endoglucanase (both from Trichoderma sp). Baking trials were conducted on small (100 g) as well as commercial (700 g) scale. Quality characteristics evaluated included dough quality, bread weight, bread height, bread volume, softness of crumb, bread slice characteristics and overall crumb texture. All the results were compared to a control. From the results of the small-scale baking trials both the pure and commercial endoxylanases significantly (P<0.05) improved bread height and softness of crumb, with the pure endoxylanase also increasing slice brightness. Both the pure and commercial endoglucanases significantly (P<0.05) increased softness of the crumb and slice brightness. When the enzymes were evaluated in combination, only an increase in bread height was observed for some of the combinations. From the results of the baking trials conducted on commercial scale, the loaf height was significantly (P<0.05) increased by the pure endoxylanase and the pure endoglucanase, while the bread volume was significantly (P<0.05) increased by all the enzymes being tested. Enzyme combinations resulted only in a significant (P<0.05) increase in bread volume. The texture of the bread crumb was significantly (P<0.05) influenced by the commercial endoxylanase, the pure endoxylanase, the pure endoglucanase as well as two of the enzyme combinations, resulting in a more open and coarse crumb texture. Slice brightness was significantly (P<0.05) decreased by the commercial endoxylanase, the pure endoxylanase, the pure endoglucanase as well as the two enzyme combinations. Both endoxylanases and endoglucanases can therefore be used to improve bread quality characteristics such as bread height and/or volume, slice brightness and softness of crumb. However, using pure enzymes specific characteristics can be targeted. This would become more feasible if pure or single component enzymes become more readily available and cost effective to use. Apart from testing the effect of the enzymes on bread quality characteristics using small-scale baking trials, it was shown in this study that testing of enzymes could also be efficiently conducted on commercial scale. In the latter the enzymes were being tested using commercial white bread flour as well as a leaner formulation. The leaner formulation allowed for the effect of the enzymes to be observed more prominently. The benefit of the evaluation on commercial scale was that the effect of the enzymes was tested in a process similar to that used in industry.

Thesis (Msc Food Sc (Food Science))--Stellenbosch University, 2008. / Carob (Ceratonia silliqua) is an evergreen, drought resistant tree of Mediterranean origin. Popularly known as St John’s bread, the carob pod has a long history of use in food (over 4 000 years). Carob has a good nutritional value, a long shelf-life (2-3 years) and it is relatively cheap. Due to its high sugar content, carob is naturally sweet. It also has a nutty chocolate-like flavour, but unlike chocolate or cocoa, carob does not contain any caffeine, thiobromine or oxalic acid. In addition, carob is normally regarded as a healthy food because of its low fat content (0.2 – 2.3%). Carob trees are also found in South Africa, especially in the Western Cape Province. Locally, carob trees have been used mainly ornamentally or as a source of animal fodder, with minimal use of the pods as a nutritious food source. Knowledge of the nutritional composition and the overall nutritional potential of locally (South African) grown carob cultivars is also limited. Carob could potentially be used as an alternative food source in South Africa as currently, most of this nutritious product goes to waste each year. In this study, the feasibility of using carob pods as an alternative source of food in South Africa was investigated. This was done by firstly, analysing the cultivars for proximate composition (moisture, carbohydrates, sugars, dietary fibre, protein, polyphenols, fat and ash) as well as for amino acids, fatty acids and minerals, in order to determine and compare their nutritional contents. Five cultivars (Tylliria, SFax, Aaronsohn, Santa Fe and an “Unknown” cultivar) were examined. The average proximate composition of raw carob pods was 8.17 – 9.56% moisture, 89.57 – 91.12% carbohydrates, 40.69 – 54.74% total sugars (33.70 – 45.09% sucrose, 1.79 – 4.95% glucose and 1.80 – 5.19% fructose), 29.88 – 36.07% dietary fibre, 3.07 – 4.42% protein, 2.58 – 3.08% polyphenols, 0.45 – 0.86% fat and 2.13 – 2.69% ash. Seven essential amino acids were present in all the cultivars, except for methionine which was not detected in the Single unknown cultivar. This study has shown that all the cultivars had good long-chain fatty acid (LCFA) proportions in terms of the saturated to polyunsaturated fatty acid (SFA: PUFA) and n-6 to n-3 ratios. The short-chain fatty acid content of the cultivars was low. All nine minerals (calcium, phosphorus, potassium, magnesium, sodium, manganese, iron, copper and zinc) analysed for in this study were detected in all five carob cultivars and all cultivars were very low in sodium. The impact of various roasting times (45, 60 and 75 min) at 150ºC, on the temperature sensitive components such as sugars, protein and fat, was also examined. Roasting had no significant (P>0.05) effect on the fat content. Although roasting significantly (P<0.05) reduced the sugar and protein content from 54.74 to 32.53% and 3.59 to 3.18%, respectively, levels in both raw and roasted carob still represented a potentially nutritious food source and alternative to cocoa. A variety of food products targeted at the various food market sectors were developed with carob as an ingredient. The formulations for five new food products (bread, porridge, breakfast cereal, mousse and milk-based drink) were developed where carob had successfully been incorporated as an ingredient. Microbiological and consumer sensory analyses carried out showed that all products developed were safe and acceptable. The findings of this study provide useful scientific evidence towards the fact that carob could potentially be used as an alternative food source in South Africa.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2006. / Fruit juices were until recently considered to only be susceptible to spoilage by yeasts, mycelial fungi and lactic acid bacteria. Spoilage by these organisms was prevented by the acidic pH of fruit juices and the heat-treatment applied during the hot-fill-hold process. Despite these control measures, an increasing number of spoilage cases of fruit juices, fruit juice products and acidic vegetables due to contamination by thermophilic acidophilic bacteria (TAB) have been reported. The genus Alicyclobacillus, containing TAB were first classified as Bacillus, but were reclassified in 1992. Species of Alicyclobacillus are Gram-positive, rod-shaped, endospore-forming bacteria. The unique characteristic of these organisms is the presence of ω-alicyclic fatty acids, such as ω-cyclohexane and ω-cycloheptane, as the major components of the cellular membrane. This organism has been shown to survive pasteurisation conditions of 95°C for 2 min and grows within a pH range of 2.5 to 6.0 and temperatures between 25° and 60°C. The genus currently consists of 11 species, with A. acidoterrestris, A. acidocaldarius and A. pomorum being the only species associated with the spoilage of fruit juices and fruit juice products. The aim of this study was to evaluate culture-dependent and culture-independent approaches for the detection and isolation of Alicyclobacillus spp. from pasteurised South African fruit juices and concentrates. The culture-dependent approach was evaluated by comparing five different growth media, for growth and recovery of A. acidoterrestris, A. acidocaldarius and A. pomorum at different incubation temperatures, from sterile saline solution (SSS) (0.85% (m/v) NaCl), diluted and undiluted fruit juice concentrates. The five media evaluated included potato dextrose agar (PDA), orange serum agar (OSA), K-agar, yeast extract (YSG)-agar and Bacillus acidocaldarius medium (BAM). The culture-independent approach was used to identify the micro-organisms present in fruit juices and concentrates from different South African manufacturers before and after pasteurisation, using polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. Spread plates of PDA at pH 3.7 and incubation temperature of 50°C for 3 days was found to be the best isolation media for species of Alicyclobacillus from fruit juice and fruit juice concentrate. With the inclusion of a heat shock treatment at 80°C for 10 min the growth media of preference for spores of Alicyclobacillus from fruit juice concentrates was OSA at pH 5.5 and an incubation temperature of 50°C for 3 days. The culture-dependent approach could detect cells or endospores at a minimum concentration of 104 cfu.ml-1 in SSS and diluted fruit juices. PCR-based DGGE analysis was more sensitive and detected cells of Alicyclobacillus spp. from fruit juices and concentrates at a minimum concentration of 103 cfu.ml-1. Alicyclobacillus acidoterrestris was found to be present in South African apple juice, pear juice, white grape juice and aloe vera juice. White grape juice was also found to contain A. pomorum. Other organisms present in the orange, apple, mango and pear juices were two uncultured bacteria that were identified as members of the genus Bacillus, and one uncultured bacterium closely related to Alcaligenus faecalis. This study confirmed the presence of TAB in pasteurised South African fruit juices and concentrates and emphasises the need for the rapid and accurate detection of TAB in food products.

Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Fresh ostrich meat competes in well regulated and competitive international markets; therefore food quality and safety are of the utmost importance. At the same time the production process must be well controlled to be cost effective. Losses in meat yield through bruising and the trimming thereof as well as a high initial microbial load that causes a decrease in shelf-life is thus undesirable. The main objectives of this study were firstly to investigate the expected prevalent microbial growth on ostrich meat as well as possible environmental contaminants to establish which bears the greatest risk. Secondly to establish the best practice of removing bruised areas from carcasses from both a microbiological and meat yield perspective. Lastly to investigate bruises on carcasses to predict the possible causes thereof so as to minimize bruising during transport and handling. From this study it was concluded that the prevalent growth on carcasses was predominantly Grampositive which increased ten fold from post-evisceration to post-chilling, this was also associated with a marked increase in Gram-negative organisms. The most dangerous vector for contamination was found to be standing water containing Gram-negative human pathogens including Shigella, Salmonella and E. coli. Bruises to the necks (52.58% of all bruises) were the most frequent, the high side railings on transport trucks the probable cause thereof. It was indicated that aerobic viable counts decreased after cold trimming, where the opposite occurred on warm trimmed surfaces, while the average loss in meat yield per bird due to bruising was smaller for cold trimming. / AFRIKAANSE OPSOMMING: Vars volstruisvleis kompeteer in goed gereguleerde en kompeterende internasionale markte; dus is voedselkwaliteit en –veiligheid baie belangrik. Terselfdertyd moet die produksieproses goed beheer word en koste effektief wees. Verliese aan vleisopbrengs as gevolg van kneusings en die verwydering daarvan, sowel as ‘n hoë inisiële mikro-organisme lading wat ‘n verkorte rakleeftyd tot gevolg het, is dus ongewens. Die hoofdoelwitte van die studie was eerstens om die verwagte mikro-organisme groei op volstruisvleis en op moontlike omgewings kontaminasie bronne te ondersoek om vas te stel watter bronne die grootste risiko dra vir besmetting. Tweedens om die beste praktyd vir die verwydering van kneusings van die volstruiskarkasse te bepaal uit beide ‘n mikrobiologiese en vleisopbrengs oogpunt. Laastens om die omvang en verspreiding van karkaskneusings te ondersoek om die oorsaak daarvan te probeer aandui en sodoende kneusings tydens vervoer en hantering te verminder. Uit die studie was die volgende duidelik; die mikrobiese groei op karkasses was hoofsaaklik Gram-positief, tellings het tienvoudig toegeneem vanaf ontweiding tot na verkoeling, met ‘n gepaardgaande merkbare toename in Gram-negatiewe organismes. Die gevaarlikste oorsaak van omgewingskontaminasie was staande water wat Gram-negatiewe menslike patogene (insluitend; Shigella, Salmonella en E. coli) bevat het. Nekkneusings (52.58% van all kneusings) was die algemeenste; met die hoogte van die kantreëlings van die volstruistrokke die moontlike oorsaak daarvan. Dit is bewys dat die aerobe mesofiele plaattelings afgeneem het na koue verwydering, maar dat die teenoorgestelde gesien is op warm gesnyde areas; die gemiddelde verlies in vleisopbrengs per volstruis as gevolg van kneusingverwydering is kleiner tydens koue verwydering.

Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Fermented fish products are popular food products mainly consumed and produced in Southeast Asia. These products are not produced in South Africa, and those available to the public are imported. The main action during the production and fermentation of this sort of product, is that of proteolysis, either by the bacteria or enzymes naturally present in the fish. The prevalent microbes present in six fermented fish samples from Bangkok (Thailand) and seven from Khon Kaen (Thailand), were determined, and using numerical methods, clustered into similarity groups using the calculated dendrogram .distance (Do) technique to determine their relation to reference strains. Forty-seven different bacterial strains were isolated, but no yeasts, moulds or lactic acid bacteria were found. Five Gram-negative, oxidase-positive species, five different Staphylococcus species and nine different endospore-forming species of the genus Bacillus, were isolated and identified using the API systems. The data indicated that members of the genus Bacillus were the prevalent organisms in all the products examined. The isolates were also scanned for general enzyme activity using the API Zym technology, and the production of proteases was investigated using the Standard Methods Caseinate and the Universal Protease Substrate methods. It was found that most of the isolated organisms produced protease, which is of major importance in the production of fermented fish products. Proteolytic cultures from the fermented fish products, as well as lactic acid starters, were used in the production of a fermented fresh water fish product. Production parameters including: glucose, inoculum, moisture content and incubation time, were evaluated in order to select optimum fermentation conditions. Fermentation efficiency was determined by measuring the final pH, titratable acid and the free amino nitrogen content. Optimum efficiency was obtained with 5% (w/w) added glucose at a moisture level of 150 ml water per 100 g fish. A factorial design (3 x 3 x 3) was used to indicate viable trends to facilitate optimisation of the fermentation process. The main effects, two-factor and three-factor interactions were calculated. Optimum trends obtained were a glucose concentration of 5% (wlw) , inoculum concentration of 1x10⁸ kve.ml ̄ ¹, an incubation period of 15 days and temperature of 30°C. Three lactic acid starters (226 - Lactobacillus plantarum, 140 - Lactococcus diacetylactis and 407 - Pediococcus cerevisiae) were selected as they produced some of the best fermentation results and are safe to use in food. It was found that a combination of all three strains (226, 140 and 407) yielded the best results. By using the above parameters, an acceptable product was produced in terms of consistency, colour and aroma. Further studies need to be conducted to optimise the safety of the product as well as the flavour, both chemically and sensorically optimisation of the product. / AFRIKAANSE OPSOMMING: Gefermenteerde visprodukte is populere voedselprodukte in die lande van Suidoos-Asie. Die produkte word nie in Suid-Afrika geproduseer nie, maar slegs ingevoer. Die hoof aksie tydens die fermentasie proses is proteolise deur die bakteriee en ensieme wat natuurlik teenwoordig is in vis. Die oorheersende mikrobes teenwoordig in ses gefermenteerde vis produkte van Bangkok (Thailand) en sewe van Khon Kaen (Thailand), is bepaal. Numeriese metodes is gevolg om die isolate in groepe te sorteer en te groepeer deur gebruik te maak van die berekende dendrogram afstand (Do) tegniek om hul verwantskap ten opsigte van die verwysingsorganisme te bepaal. Sewe-en-veertig verskillende bakteriee is ge·isoleer, maar geen fungi of melksuurbakteriee is ge·identifiseer nie. Vyf Gram-negatiewe, oksidase-positiewe spesies, vyf verskillende Staphylococcus spesies en nege verskillende endospoorvormende spesies van die genus Bacillus, is geisoleer en ge·identifiseer deur gebruik te maak van die API CHB sisteme. Die data het getoon dat lede van die genus Bacillus die oorheersende organismes was. Die isolate is daarna ondersoek vir algehele ensiemaktiwiteit deur van die API Zym tegnologie gebruik te maak. Daar is veral klem gelê op die protease aktiwiteit en dit is gemeet deur van die "Standard Methods Caseinate Agar" metode asook die "Universal Protease Substrate" metodes gebruik te maak. Daar is gevind dat die oorgrote meerderheid organismes proteolitiese ensieme produseer wat belangrik is in die produksie van gefermenteerde visprodukte. Kulture wat ge·isoleer is uit gefermenteerde visprodukte asook melkssuurkulture is gebruik vir die produksie van 'n gefermenteerde varswater visproduk. Produksieparameters insluitende: glukose-, inokulum- en voginhoud asook inkubasie tyd is ondersoek om die optimum fermentasie kondisies te bepaal. Optimum effektiwiteit is gevind by 'n 5% glukose konsentrasie en vogvlakke van 150 ml water per 100 9 vis. 'n Faktoriale ontwerp (3 x 3 x 3) is gebruik om die optimum kondisies te bepaal. Die hoof effekte asook die twee faktor en drie faktor interaksies is bereken. Optimum neigings is gevind by 'n glukose konsentrasie van 5%, inokulum konsentrasie van 1x10⁸ kve.ml ̄ ¹, 'n inkubasie tydperk van 15 dae en temperatuur van 30°C. Drie melksuurbakteriee (226 - Lactobacillus plantarum, 140 - Lactococcus diacetylactis en 407 - Pediococcus cerevisiae) is gekies aangesien hulle die beste resultate gelewer het en veilig vir gebruik in voedselprodukte is. Daar is gevind dat die drie melksuurkulture saam in kombinasie die beste fermentasie resultate opgelewer het. Deur gebruik te maak van die bogenoemde fermentasie kondisies, kon 'n aanvaarbare produk, in terme van kleur en geur, gelewer word. Verdere studies moet gedoen word om die veiligheid asook die geur, chemies asook sensories, te optimiseer.

Thesis (MSc Food Sc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Maas is a traditional fermented milk drink of the indigenous people of Southern Africa and can thus be used to uplift the nutritional status of the South African population, especially for the lower income groups. Furthermore, the problem of lactose intolerance among the Black population can also be addressed by the consumption of Maas. The objective of this study was to screen mesophylic lactic acid bacterial strains (25 in total) from the University of Stellenbosch Food Science Culture Collection for suitable metabolite production and then to produce traditional Maas with a starter culture combination that produces a distinctive acid and traditional flavour. The representative 25 single lactic acid starter strains were identified as Lactococcus lactis subsp. leetis biovar diacetylactis (12 strains), L. leetis subsp. leetis (four strains) and L. leetis subsp. cremoris (nine strains). These strains were inoculated into pasteurised full cream milk and activated for 8 h at 22°C. Pasteurised full cream milk was then inoculated with each of the activated starter strains, incubated at 22°C for 16 h and assessed for acid production abilities (pH = 4.6) under controlled time-temperature conditions. The results of this study showed that nine of the single strains, L. lactis subsp. leetis biovar diacetylactis (S1, S2, S3 and S5), L. teetis subsp. lactis (S13, S15 and S16) and two L. leetis subsp. cremoris strains (S17 and S22), produced sufficient acid, rendering them suitable for the use as starters in the production of traditional Maas. A pH range of 4.3 - 5.1 was reached by the nine single strains after 16 h at 22°C. Two-strain starter combinations were then formed by combining the most suitable single L. leetis subsp. leetis biovar diacetylactis, L. lactis subsp. lactis and L. lactis subsp. cremoris strains, respectively. From the data, it was concluded that acceptable Maas could be produced with four two-strain combinations (S3S 17, S3S22, S5S17 and S5S22). This selection was again based on suitable acid and metabolite production, as well as on sensory evaluation of the final product. These four two-strain combinations produced sufficient acid to reach a pH in the 4.6 - 4.8 range, and showed a high metabolite concentration for the most suitable compounds and formed a thick, smooth and creamy body texture after 16 h at 22°C. Three-strain combinations formed between the two-strain starter combinations and L. leetis subsp. teetis strains (813, 815 and 816), were also evaluated. With these combinations a lack of a pronounced Maas flavour was found. Thus, it was decided to add aroma producing strains of the species Leuconostoc mesenteroides subsp. dextranicum (strain L1) and L. mesenteroides subsp. citrovorum (strain L2) to the three-strain combinations. Four culture combinations (A, B, C and D) were then formed by combining the selected Leuconostoc strains (L1 and L2) with the most suitable Lactococcus strains (83,817,813 and 822). These combinations produced sufficient acid to reach the pH 4.5 - 4.6 range after 14 h at 22°C. Acetaldehyde was the major flavour metabolite formed in the Maas made with these four combinations, with concentrations ranging between 26.6 - 89.3 mg.l ̄ ¹, while other flavour metabolites (ethanol, acetone, diacetyl and 2-butanone) were present at lower concentrations. It was found that three of the four culture combinations (A, C and D) were characterised by a superior, but delicate flavour and a typical characteristic Maas body texture. Fruit flavoured Maas was subsequently prepared with the three most suitable culture combinations (A, C and D) using 11 flavours and a sensory evaluation performed. The statistically evaluated data showed that the appearance, smoothness, flavour intensity, sweetness and overall acceptability were influenced by the type of fruit flavour and the culture combination. Fruit flavour 4 (banana) was the most preferred flavour. The sensory panellists also indicated that the culture combination C gave the best overall acceptability over a three week study period. Data on the shelf-life study of natural unflavoured Maas, prepared with the three culture combinations (A, C and D), showed that the Maas still had an acceptable appearance, taste and good microbiological quality after 15 d at refrigerated temperatures. / AFRIKAANSE OPSOMMING: Maas is 'n tradisionele gefermenteerde melkdrankie onder die inheemse bevolking van Suid-Afrika en kan gebruik word om die voedingstatus van die Suid-Afrikaanse bevolking te verhoog, veral vir die laer inkomste groepe. Bowendien, kan die probleem van laktose intoleransie onder die Swart gemeenskap ook aangespreek word deur die verbruik van Maas. Die doel van hierdie studie was om enkelstam mesofiliese melksuur bakterieë (25 in totaal) van die Universiteit van Stellenbosch Voedselwetenskap Kultuur Versameling te ondersoek vir geskikte metaboliet produksie en tradisionele Maas met 'n kenmerkende suurheid en tradisionele geur met 'n geskikte kultuur kombinasie te produseer. Die toonaangewende 25 enkelstamme is Lactococcus lactis subsp. leetis biovar diacetylactis (12 stamme), L. lactis subsp. lactis (vier stamme) en L. lactis subsp. cremoris (nege stamme). Hierdie stamme was in gepasteuriseerde volroom melk geïnokuleer en geaktiveer vir 8 h teen 22°C. 'n Inokulum van die onderskeie geaktiveerde stamme is hierna in gepasteuriseerde volroom melk geplaas, vir 16 h teen 22°C geïnkubeer en hul vermoë om suur te produseer (pH = 4.6) onder beheerde tyd-temperatuur kondisies is bepaal. Die resultaat van die studie het aangedui dat nege enkelstamme, naamlik L. leetis subsp. lactis biovar diacetylactis (S1, S2, S3 en S5), L. lactis subsp. leetis (S13, S15 en S16) en twee L. leetis subsp. cremoris (S 17 en S22), geskikte suurheidsvlakke vir die produksie van Maas bereik het. 'n pH vlak van 4.3 - 5.1 is na 16 h teen 22°C deur hierdie nege enkelstamme bereik. Twee-stam kombinasies is onderskeidelik gevorm tussen die geskikte enkel L. lactis subsp lactis biovar diacetylactis, L. lactis subsp. lactis en L. lactis subsp. cremoris stamme. Die gevolgtrekking gemaak uit die data, is dat aanvaarbare Maas voorberei kan word met vier van die twee-stam kombinasies (S3S17, S3S22, S5S17 en S5S22) op grond van suurvorming, metaboliet produksie en sensoriese evaluasie. Hierdie vier kombinasies het genoegsame suur geproduseer om 'n pH vlak van 4.6 - 4.8 bereik, hoë metaboliet konsentrasies geproduseer en 'n dik, gladde en romerige tekstuur aangeneem na 16 h teen 22°C. Drie-stam kombinasies is gevorm tussen die onderskeie twee-stam kombinasies en L. lactis subsp. lactis stamme (813,815 en 816) en ook geëvalueer. Die tekort aan 'n skerp Maas geur in die drie-stam kombinasies het daartoe gelei dat Leuconostoc mesenteroides subsp. dextranicum (stam L1) en L. mesenteroides subsp. citrovorum (stam L2) bygevoeg is. Vier kultuur kombinasies (A, B, C en D) is gevorm deur die geselekteerde Leuconostoc stamme (L1 en L2) te kombineer met die mees gepaste Lactococcus stamme (83, 817, 813 en 822). Hierdie kombinasies het genoegsame suur geproduseer wat 'n pH vlak van 4.5 - 4.6 na 14 h teen 22°C bereik het. In die Maas wat met bovermelde kombinasies gemaak is, was die asetaldehied die mees geproduseerde geur metaboliet teen konsentrasies van 26.6 - 89.3 mg.l ̄ ¹. Ander geur metaboliete (etanol, asetoon, diasetiel, 2-butanoon) is in laer konsentrasies geproduseer. Daar is gevind dat drie uit die vier kultuur kombinasies (A, C en D) 'n superieur, delikate geur wat 'n tipies karakteristiek van die Maas gehad het. Vrugte gegeurde Maas geproduseer met die drie kultuur kombinasies (A, C en D) deur 11 geursels te gebruik, is sensories geëvalueer. Die statistiese geëvalueerde data het getoon dat die voorkoms, gladheid, geur intensiteit, soetheid en die algehele aanvaarbaarheid beïnvloed is deur die tipe vrugte geursels en die kultuur kombinasies. Die vrugte geursel 4 (piesang) het voorkeur geniet. Die sensoriese paneellede het ook aangedui dat kultuur kombinasie C die algehele mees aanvaarbare Maas geproduseer het oor die studie periode van drie weke. Data van die rakleeftyd van die natuurlike ongegeurde Maas wat geproduseer is met die drie kultuur kombinasies (A, C en D) het aangedui dat die Maas na 15 d by yskas temperatuur steeds 'n aanvaarbare voorkoms, smaak en goeie mikrobiologiese kwaliteit gehad het.

Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Kepi is a refreshing, fermented dairy beverage that has been consumed for centuries and is traditionally made by incubating Kepi grains in milk. The Kepi grain is a complex starter culture consisting of a variety of lactic acid bacteria and yeasts. The successful marketing of the grains requires the effective preservation of the microbes present in the grains as well as an appropriate packaging that will retain the acidification activity of the preserved grains over an extended period of time. The aim of this study was to evaluate different preservation techniques and packaging materials in terms of their respective abilities to retain grain viability and activity over an extended storage period. Four different preservation techniques (freezing at -18°C, refrigeration at 4°C, air-drying and Iyophilisation) and three packaging materials including a low density polyethylene film (LOPE), an oriented polyester film (OPET) and a metallised oriented polyester film (MOPET), were evaluated. Activity tests were used to evaluate the impact of the preservation techniques in terms of the retainment of the acidification activity of the preserved grains, and the storage potential of the preserved and packaged grains. The activity tests included changes in pH, %TA, lactic acid production and lactose and volatile compound content over an 18 h fermentation period. In addition, the microbial viability of the packaged Iyophilised grains after two months of storage, was also investigated. Frozen and refrigerated grains showed the best retainment of the acidification activity over a 10-month storage period. Air-drying and Iyophilisation showed a good retention of the activity up to three months of storage, but the application of these techniques both resulted in a retarded initial acidification activity. After 10 months of storage, the air-dried and Iyophilised grains showed only a low acidification activity. No volatile compounds could be detected during the course of the fermentation period, due to the relative short fermentation period of 18 h. Overall, the best retainment of the fermentation activity was given by the LOPE and the OPET packaging films. However, the storage period had a considerable influence on the retention of the activity of the packaged Iyophilised grains. The viability study of the Iyophilised packaged Kepi grains after two months of storage showed leuconostocs and lactobacilli to be the prevalent microbes in the grains. Low microbial counts were obtained from the lactococciselecting medium for all three of the differently packaged Kepi grains, whereas no growth was observed on the media that selected for the propionibacteria and yeasts. The OPET packaging film provided the best preservation of the microbial composition. It was, therefore, concluded that all four preservation techniques would be suitable for the preservation of Kepi grains and the subsequent storage at room temperature for three months. However, for storage periods of 10 months or longer the use of freezing and refrigeration are recommended as most suitable preservation techniques. All three of the packaging materials proved to be suitable for the packaging and storage of the Iyophilised Kepi grains for periods of up to one month. However, for storage periods of two months or longer, the use of the OPET film for the packaging and retainment of the acidification activity of the Iyophilised grains, can be recommended. / AFRIKAANSE OPSOMMING: Kepi is 'n eeu-oue verfrissende, gefermenteerde suiweldrankie wat tradisioneel vervaardig word deur Kepikorrels in melk te inkubeer. Hierdie Kepikorrels bestaan uit 'n komplekse samestelling van hoofsaaklik melksuurbakteriee en giste. Die effektiewe preservering en verpakking van die korrels is belangrike voorvereistes vir die suksesvolle bemarking daarvan. Dis belangrik dat die preserverinq en die verpakking van die korrels 'n positiewe bydrae sal lewer tot die behoud van die fermentasie-aktiwiteit van die mikrobes in die korrels oar 'n verlengde opbergingsperiode. Die doel van hierdie studie was om die opbergingspotensiaal van verskillend gepreserveerde en -verpakte Kepikorrels te evalueer in terme van die behoud van die lewensvatbaarheid en fermentasie-aktiwiteit van die samestellende mikrobes. Vier verskillende preserveringstegnieke (bevriesing by -18°C, verkoeling by 4°C, lugdroging en vriesdroging) en drie verskillende tipes verpakkingsmateriale, nl. 'n "low density polyethylene film" (LOPE), 'n "oriented polyester film" (OPET) en 'n "metallised oriented polyester film" (MOPET) was qeevalueer. Aktiwiteitstoetsing was gebruik om die impak van die verskillende preserveringstegnieke en die verpakkingsmateriale op die behoud van die fermentasie-aktiwiteit van die Kepikorrels te ondersoek. Die verskillende aktiwitieitstoetse wat gedoen is, het die meting van die verandering in pH, %TA, melksuur- en laktosekonsentrasie oor 'n fermentasieperiode van 18 h ingesluit. Tesame met die aktiwitietstoetsing IS die lewensvatbaarheid van die gevriesdroogde, verpakte Kepikorrels na twee maande van opberging ook ondersoek. Die bevrore en verkoelde Kepikorrels het die beste behoud van aktiwitiet na 'n 10-maande opbergingsperiode getoon. Die gelugdroogde en gevriesdroogde korrels het 'n goeie behoud van aktiwiteit getoon vir 'n opbergingstydperk van tot drie maande, maar beide die lugdroging- en vriesdrogingstegnieke het 'n aanvanklik vertraagde fermentasie-aktiwitieit getoon. Na 'n : opbergingsperiode van 10 maande het beide die gelugdroogde en gevriesdroogde korrels egter 'n lae fermentasie-aktiwiteit getoon. As gevolg van 'n relatiewe kort fermentasieperiode van 18 h kon geen vlugtige komponente in die Kepimonsters gevind word nie. Die LDPE- en OPET-verpakkingsmateriale het die beste behoud van die fermentasie-aktiwiteit van die gevriesdroogde korrels getoon. Die opbergingsperiode het egter 'n aansienlike impak op die aktiwitietsbehoud van die korrels gehad. Die lewensvatbaarheidstudie het aangetoon dat Leuconostoc- en Lactobacillus-spesies die oorheersende mikrobes in die verpakte, gevriesdroogde Kepikorrels na 'n opbergingsperiode van twee maande was. Lae mikrobiese tellings vir al drie van die verpakkingsmateriale was gevind op die Lactococcusselekterende medium, en geen mikrobegroei kon op die giste- en propionibakteriee-selekteringsmedium waargeneem word nie. Die beste behoud van die mikrobiese samestelling in die verpakte, gevriesdroogde Kepikorrels was gevind vir die OPET-verpakkingsmateriaal. Die gevolgtrekking kan gemaak word dat al vier die preserveringstegnieke geskik is vir die preservering van die Kepikorrels en die daaropvolgende opberging van drie maande by kamertemperatuur. Vir opbergingsperiodes van 10 maande en langer word die gebruik van bevriesing en verkoeling aanbeveel as die mees geskikte preserveringstegnieke. AI drie verpakkingsmateriale kan gebruik word vir die verpakking en opberging van gevriesdroogde Kepikorrels vir 'n tydperk van een maand. Indien 'n opbergingsperiode van twee maande of langer verlang word, word die OPET-verpakkingsmateriaal aanbeveel vir die suksesvolle behoud van die fermentasie-aktiwiteit van die Kepikorrels.