Thesis (MSc Food Sc (Food Science))--University of Stellenbosch, 2009. / This study focused on a serious quality-related problem in the global wine industry, including the South African Wine Industry, namely cork taint in wine. Annually, large financial losses are incurred by cork suppliers and wine producers, as a result of cork-tainted wine. Although contaminated new unused corks are frequently implicated as the origin of this taint, contaminated cellar equipment and water can also be the source of the problem. An explorative investigation into the incidence of cork taint in South African wines showed that 3.8% of the 133 wines tested, contained 2,4,6-trichloroanisole (TCA) concentrations of 3.5 ng/L and higher, as determined by gas chromatography coupled with electron capture detection (GC-ECD). TCA concentrations higher than 1 ng/L were found in 18% of the wines tested. All affected wines were sealed with solid or agglomerate cork stoppers. These wines were sourced from various wineries in the Western Cape region, South Africa and were of different cultivars. None of the wines sealed with synthetic closures had any detectable TCA, 2,4,6-tribromoanisole (TBA) or pentachloroanisole (PCA) levels and only very low 2,3,4,6- tetrachloroanisole (TeCA) levels (1 ng/L or less). Another group of 28 wines that were rejected by the official South African wine regulatory body on the basis of the presence of mouldy taint during wine certification, was also included in this study. GC-ECD analysis showed that 30% of the wines in this group contained TCA at concentrations of 3.5 ng/L and higher. These results pointed to a relative high incidence of TCA in the wines investigated, especially those sealed with cork stoppers. Although no general conclusions should be made on the incidence of cork taint in the wider wine industry based on the results found within this explorative investigation, these findings confirmed the presence of cork taint in South African wines. Detection threshold values were determined for TCA, TeCA, TBA and PCA in three wine cultivars using the standard ASTM method. Results indicate that factors relating to the wine cultivar seemed to affect threshold values considerably. Our research proposes a detection range rather than an average detection threshold. Detection ranges established for TCA, TeCA, TBA and PCA in Chenin blanc, Pinotage and Shiraz coincide with reported values in literature. This result can be regarded as a valuable expansion of the existing knowledge of detection threshold values. Descriptive sensory analysis indicated significant (P 0.05) changes in the aroma profile of Chenin blanc, Pinotage and Shiraz after TCA, TeCA, TBA or PCA was added to the respective base wines that contained no detectable levels of the haloanisoles. The mouldy taint induced by these haloanisoles were described as mouldy, mouldy-chemical, mouldychlorine, as well as mouldy-acidic. In Chenin blanc, additions of TCA, in the concentration range 1 to 17 ng/L, resulted in a marked increase in the mouldy aroma and was accompanied by an immediate decrease in fruitiness. This change was already evident at added TCA concentrations of 1 ng/L. Similar trends were observed in Pinotage, while the addition of low levels of TCA to Shiraz (2 ng/L) resulted in a significant (P 0.05) decrease in the herbaceous character of the wine. The aroma changes observed were prominent enough to render the wine totally unacceptable in comparison to its original character. Consumers’ degree of liking did not seem to be affected by very low concentration levels of TCA in Chenin blanc, Pinotage or Shiraz, but rejection increased as the concentration increased beyond detection threshold level. A slight gender effect was also noticed. Female consumers appeared to be more sensitive to increasing levels of TCA, whereas male consumers did not respond as negatively to higher concentration levels of TCA. This study makes an important contribution towards understanding the sensory impact of especially TCA contamination in wine, through the establishment of concentration ranges at which these compounds exert a noticeable detrimental effect on the aroma profile of wine. Additional insight into cork taint in wine is provided by the consumer preference studies, where the effects of the taint on the product acceptance by consumers are demonstrated. The development of a modus operandi to ensure that sensory panels provide reliable data, can be regarded as an important contribution to wine-related research. This study is one of the first where advanced sensometric techniques were applied in sensory studies on cork tainted wines.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / Triticale (X Triticosecale Whittmack), a cross between durum wheat (Triticum sp.) and rye, is a crop with an increasing agronomic and economic potential Though studies on the functional and compositional quality of triticale have been conducted in other parts of the world, little is known regarding cultivars developed in South Africa in terms of these aspects. South African triticale cultivars from various localities in the Western Cape, obtained for two subsequent harvest seasons, were analysed for moisture, protein and ash contents, as well as falling number (an indication of α-amylase activity), hardness (particle size index), 1000-kernel mass and baking potential (SDS sedimentation). These triticale samples were derived from a breeding program that was not focused on baking quality. The results obtained were found to compare well with those reported on in previous studies. Significant differences were observed between both cultivars and localities within years, illustrating the effect of genetic as well as environmental factors. Significant differences were also observed between localities when comparing the two harvest seasons, whereas differences between the cultivars for the two seasons were in most cases not significant; illustrating the effect of environment. Interactions between cultivars and localities were found to be significant for all parameters, and trends were observed between protein content and both particle size index (PSI) (negative) as well as SDS sedimentation (positive) results for both years. Near infrared (NIR) spectroscopy is a rapid method of analysis and is widely used for the quality evaluation of wheat. Limited research has been reported on calibration models for the quality evaluation of triticale, and thus NIR spectroscopy was applied to develop models for the prediction of moisture, protein and ash contents, as well as hardness and baking potential for South African cultivars. Spectra were collected in diffuse reflectance mode and partial least squares (PLS) models developed for both triticale flour and wholegrain using two different instruments (Büchi NIRFlex N-500 and Bruker MPA Fourier transform NIR spectrophometers) and software packages (The Unscrambler and OPUS). Full cross-validations were performed, after which the best prediction models obtained (R2 > 0.66) were validated using an independent test set (n = 50). The best prediction results were obtained with flour for moisture (Bruker: SEP = 0.08%; R2 = 0.95; RPD = 4.65) and protein (Büchi: SEP = 0.44%; R2 = 0.96; RPD = 5.23 and Bruker: SEP = 0.32%; R2 = 0.96; RPD = 4.88). For whole grain, acceptable results were obtained for protein (Büchi: SEP = 0.55%; R2 = 0.94; RPD = 4.18 and Bruker: SEP = 0.70%; R2 = 0.90; RPD = 3.23). Though results for ash content, PSI and SDS sedimentation prediction did not yield models that can be applied as yet, these models form a good basis for further calibration model development and possibly use in early generation screening. The current limited ranges could be expanded by adding samples from subsequent harvest seasons. By adding more data, a better quality profile for South African triticale can be obtained, which will facilitate better interpretation in terms of the effect of genetic and environmental factors. It would also enable the development of improved NIR prediction models.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers that are able to spoil acidic food and beverage products through the production of guaiacol and other taint compounds, which causes a medicinal off-flavour and/or odour in the products. This thesis reports on the comparison of methods used for the isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol production of different strains isolated from the South African fruit processing environment. Two methods for guaiacol detection were also evaluated and compared. Three isolation methods frequently used by South African fruit processors were compared with regards to their ability to isolate a strain of A. acidoterrestris from diluted peach juice concentrate. Method 1, the International Federation of Fruit Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and incubation of the membrane on K agar. The IFU Method No. 12 was the most effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%. These results support the use of the IFU Method No. 12 as a standard international method for the isolation and detection of species of Alicyclobacillus. Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A. acidocaldarius FB19, were analysed based on their growth characteristics and guaiacol production under optimum conditions. Strains were inoculated into BAT medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for 7 d. All the strains had similar growth patterns, with cell concentrations increasing rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an increase in spores as the cell density and competition for resources increased. All the strains were able to produce guaiacol in detectable concentrations [as measured by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the potential to cause product spoilage. Bacteria belonging to the genus Alicyclobacillus are thermo-acidophilic spore-formers that are able to spoil acidic food and beverage products through the production of guaiacol and other taint compounds, which causes a medicinal off-flavour and/or odour in the products. This thesis reports on the comparison of methods used for the isolation of species of Alicyclobacillus, as well as the growth behaviour and guaiacol production of different strains isolated from the South African fruit processing environment. Two methods for guaiacol detection were also evaluated and compared. Three isolation methods frequently used by South African fruit processors were compared with regards to their ability to isolate a strain of A. acidoterrestris from diluted peach juice concentrate. Method 1, the International Federation of Fruit Juice Producers (IFU) Method No. 12, makes use of spread plating onto Bacillus acidoterrestris (BAT) agar plates; Method 2 involves pour plating using acidified potato dextrose agar (PDA); and Method 3 makes use of membrane filtration and incubation of the membrane on K agar. The IFU Method No. 12 was the most effective method for the isolation of A. acidoterrestris, with a recovery of 75.97%. These results support the use of the IFU Method No. 12 as a standard international method for the isolation and detection of species of Alicyclobacillus. Seven strains of Alicyclobacillus, including the type strains A. acidoterrestris DSM 3922T and A. acidocaldarius DSM 446T and five strains isolated from a South African fruit processing plant, A. acidoterrestris FB2, FB14, FB32, FB38 and A. acidocaldarius FB19, were analysed based on their growth characteristics and guaiacol production under optimum conditions. Strains were inoculated into BAT medium at pH 4.00, supplemented with 100 mg.L-1 vanillin, and incubated at 45°C for 7 d. All the strains had similar growth patterns, with cell concentrations increasing rapidly from 0-24 h, followed by a stabilisation around maximum cell concentrations of 105-107 cfu.mL-1. Cell concentrations after heat shock, measured as an indication of spore formation, increased to maximum values of 105-107 cfu.mL-1, indicating an increase in spores as the cell density and competition for resources increased. All the strains were able to produce guaiacol in detectable concentrations [as measured by the peroxidase enzyme colourimetric assay (PECA)], and, therefore, possess the potential to cause product spoilage. iv The influence of temperature on the growth and guaiacol production of the Alicyclobacillus strains was also investigated and two guaiacol detection methods, the PECA and headspace gas-chromatography mass-spectrometry (HS GC-MS), were compared with regards to their ability to detect guaiacol. The strains were incubated at 25°C and 45°C for 6 d and samples analysed every 24 h. Growth of the A. acidoterrestris strains was slower at 25°C, and maximum cell concentrations were lower than at 45°C. A decrease in cell concentrations was observed in the A. acidocaldarius strains at 25°C, as this temperature is below their growth temperature range. All the strains were able to produce guaiacol at 45°C, with guaiacol only being detected once a cell concentration of 104-105 cfu.mL-1 had been reached. The maximum guaiacol concentrations detected at 45°C in the samples containing A. acidoterrestris were significantly higher than those detected in the A. acidocaldarius samples. At 25°C there was a longer lag phase before guaiacol was detected in the A. acidoterrestris samples, while no guaiacol was detected in the samples containing A. acidocaldarius. Because guaiacol is produced at ambient temperatures, cooling of products is recommended to control spoilage by A. acidoterrestris. The sensitivity of the two guaiacol detection methods also differed significantly and, therefore, the PECA is recommended for presence/absence detection of guaiacol, while HS GCMS is recommended where accurate quantification of guaiacol is required. Alicyclobacillus acidoterrestris FB2 was investigated for its ability to grow and produce guaiacol in white grape juice supplemented with vanillin at different concentrations. Alicyclobacillus acidoterrestris FB2 was inoculated into white grape juice concentrate diluted 1:10 with distilled water containing 0-500 mg.L-1 vanillin and incubated at 45°C for 6 d. Similar growth patterns were observed in all the samples, except in the sample containing 500 mg.L-1 vanillin, which had a longer lag phase of growth. Guaiacol concentrations, detected using the PECA, increased as the vanillin concentration increased, with the exception of the sample containing 500 mg.L-1 vanillin, where less guaiacol was detected than in the sample containing 250 mg.L-1 vanillin, due to growth inhibition caused by the higher vanillin concentration. A number of conditions need to be favourable for detectable guaiacol production to occur and it could, therefore, be possible to minimise or prevent guaiacol production by controlling or eliminating some of these factors. Good manufacturing practices should be employed in order to minimise contamination and, therefore, spoilage, by Alicyclobacillus species. / AFRIKAANSE OPSOMMING: Bakterieë wat aan die genus Alicyclobacillus behoort, is termo-asidofiliese spoorvormers wat suur voedsel en drank produkte kan bederf deur die produksie van guaiakol en ander bederf verbindings, wat ‘n medisinale geur en/of reuk in die produkte veroorsaak. Hierdie tesis doen verslag oor die vergelyking van metodes wat vir die isolasie van spesies van Alicyclobacillus gebruik word, sowel as die groei kenmerke en guaiakol produksie van verskillende stamme wat uit die Suid- Afrikaanse vrugte prosesseringsomgewing geïsoleer is. Twee metodes vir die deteksie van guaiakol is ook geëvalueer en vergelyk. Drie isolasie metodes wat algemeen deur Suid-Afrikaanse vrugteprosesseerders gebruik word, is vergelyk ten opsigte van hul vermoë om H A. acidoterrestris stam uit verdunde perskesap konsentraat te isoleer. Metode 1, die Internasionale Federasie van Vrugtesap Produseerders (IFU) Metode No. 12, maak gebruik van spreiplating op Bacillus acidoterrestris (BAT) agar plate; Metode 2 behels gietplating met aartappel dekstrose agar (PDA) and Metode 3 maak gebruik van membraan filtrasie en inkubasie van die membraan op K agar. Die IFU Metode No. 12 was die mees effektiewe metode vir die isolasie van A. acidoterrestris, met H sel herwinning van 75.97%. Hierdie resultate ondersteun die gebruik van die IFU Metode No. 12 as H standaard internasionale metode vir die isolasie en deteksie van spesies van Alicyclobacillus. Sewe Alicyclobacillus stamme, insluitende die tipe stamme A. acidoterrestris DSM 3922T en A. acidocaldarius DSM 446T en vyf stamme geïsoleer uit ‘n Suid- Afrikaanse vrugte prosesseringsaanleg, A. acidoterrestris FB2, FB14, FB32, FB38 en A. acidocaldarius FB19, is geanaliseer met betrekking tot hul groei kenmerke en guaiakol produksie onder optimum toestande. Stamme is in BAT medium by pH 4.00, aangevul met 100 mg.L-1 vanillin, geïnokuleer en geïnkubeer teen 45°C vir 7 d. Al die stamme het soortgelyke groeipatrone getoon, met selgetalle wat vinnig toegeneem het van 0-24 h, gevolg deur ‘n stabilisering rondom maksimum selgetalle van 105-107 kve.mL-1. Selgetalle na hitte behandeling, gemeet as H aanduiding van spoorvorming, het toegeneem tot maksimum waardes van 105-107 kve.mL-1, wat aandui dat spore toegeneem het soos die seldigtheid en kompetisie vir voedingsbronne toegeneem het. Al die stamme kon guaiakol in bespeurbare konsentrasies produseer [soos gemeet deur die peroksidase ensiem kolorimetriese bepaling (PEKB)] en besit dus die potensiaal om produkte te bederf. Die invloed van temperatuur op groei en guaiakol produksie van die Alicyclobacillus stamme is ook ondersoek en twee guaiakol deteksie metodes, die PEKB en topspasie gas-kromatografie massa-spektrometrie (TS GK-MS) is vergelyk ten opsigte van hul vermoë om guaiakol op te spoor. Die stamme is geïnkubeer teen 25°C en 45°C vir 6 d en monsters is elke 24 h geanaliseer. Groei van die A. acidoterrestris stamme was stadiger by 25°C en maksimum selgetalle was laer as by 45°C. H Vermindering in selgetalle is waargeneem in die A. acidocaldarius stamme by 25°C, aangesien hierdie temperatuur buite hul groei temperatuur grense val. Al die stamme kon guaiakol produseer by 45°C, met guaiakol deteksie wat eers H aanvang geneem het nadat H sel konsentrasie van 104-105 kve.mL-1 bereik is. Die maksimum guaiakol konsentrasies wat by 45°C in die monsters met A. acidoterrestris opgespoor is, was beduidend hoër as die konsentrasies wat in die A. acidocaldarius monsters opgespoor is. By 25°C was daar H langer sloerfase voor guaiakol opgespoor is in die A. acidoterrestris monsters, terwyl geen guaiakol opgespoor is in die monsters wat A. acidocaldarius bevat het nie. Aangesien guaiakol by kamertemperatuur geproduseer word, word verkoeling van produkte aanbeveel ten einde bederf deur A. acidoterrestris te beheer. Die sensitiwiteit van die twee guaiakol deteksie metodes het ook beduidend verskil en dus word die gebruik van die PEKB aanbeveel vir teenwoordigheid/afwesigheid deteksie van guaiakol, terwyl TS GK-MS aanbeveel word waar akkurate kwantifisering van guaiakol vereis word. Ondersoek is ingestel na die vermoë van A. acidoterrestris FB2 om te groei en guaiakol te produseer in witdruiwesap aangevul met verskillende vanillin konsentrasies. Alicyclobacillus acidoterrestris FB2 is geïnokuleer in witdruiwesap konsentraat 1:10 verdun met gedistilleerde water wat 0-500 mg.L-1 vanillin bevat het en is geïnkubeer teen 45°C vir 6 d. Soortgelyke groeipatrone is waargeneem in al die monsters, behalwe die monster wat 500 mg.L-1 vanillin bevat het, wat H langer sloerfase van groei gehad het. Guaiakol konsentrasies, soos gemeet deur die PEKB, het toegeneem soos die vanillin konsentrasie toegeneem het, met die uitsondering van die monster wat 500 mg.L-1 vanillin bevat het, waar minder guaiakol opgespoor is as in die monster wat 250 mg.L-1 bevat het as gevolg van groei inhibisie veroorsaak deur die hoër vanillin konsentrasie. H Aantal toestande moet gunstig wees vir guaiakol produksie om plaas te vind en dit kan dus moontlik wees om guaiakol produksie te minimaliseer of te voorkom deur die beheer of uitskakeling van sommige van hierdie faktore. Goeie vervaardigingspraktyke moet in plek gestel word ten einde kontaminasie en bederf deur Alicyclobacillus spesies tot H minimum te beperk.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. / Antimutagenic activity of aqueous extracts of fermented and unfermented Cyclopia spp., i.e. C. intermedia, C. subternata, C. genistoides and C. sessiliflora against metabolically activated aflatoxin B1 (AFB1) in the Salmonella mutagenicity assay with tester strain TA100, was compared to that of fermented and unfermented Aspalathus linearis (rooibos) and Camellia sinensis (black, oolong and green) teas. Possible mechanisms involved in in vitro antimutagenic activity of these teas were investigated, i.e. the stabilising effect of the unfermented Cyclopia spp., unfermented rooibos and green tea on rat liver cytochrome P450 in the S9 fraction from Aroclor 1254 treated rats and their modulation of aniline-induced Type II difference spectra in the microsomal fraction. Inhibition of lipid peroxidation in rat liver S9, by the teas, was assessed to determine whether protection against lipid peroxidation may play a role in cytochrome P450 stability in vitro. Correlation of the antimutagenic activity of the teas with their stabilising effect on cytochrome P450 and inhibition of lipid peroxidation, provided insight into possibly related mechanisms. Antimutagenic activity correlated weakly with a decreased stabilising effect of the teas on cytochrome P450 (r = 0.411, P = 0.013) and the inhibition of lipid peroxidation (r = 0.475, P = 0.003). Decreased stability of cytochrome P450 was associated with substantial lipid peroxidation occurring in rat liver S9. Effective inhibition of lipid peroxidation and stabilising of cytochrome P450 in S9 was evident in the presence of the teas, but no correlation (r = 0.018, P = 0.915) existed for the effect of unfermented teas on cytochrome P450 stability with inhibition of lipid peroxidation. Black tea exhibited the highest protection against AFB1-induced mutagenesis and fermented C. intermedia offered the least protection. “Fermentation” resulted in increased antimutagenic activity of Camellia sinensis and rooibos teas, while the antimutagenic activity of Cyclopia spp. decreased with fermentation except for C. genistoides. Unfermented teas significantly (P < 0.05) stabilised cytochrome P450, with rooibos more effective (P < 0.05) than green tea, but similar (P < 0.05) to Cyclopia spp. Green tea demonstrated the highest inhibition of lipid peroxidation, while the inhibition exerted by rooibos was similar (P > 0.05) to unfermented Cyclopia spp., except for C. genistoides exhibiting the least inhibition. Total polyphenol, flavanol and flavonol/flavone contents of the respective teas were correlated with activity in terms of antimutagenicity, stabilising of cytochrome P450 and inhibition of lipid peroxidation. Antimutagenic activity of Cyclopia spp. correlated with its total polyphenol (r = 0.805, P < 0.0001) and flavanol (r = 0.653, P < 0.0001) contents, while a weak negative correlation (r = -0.456, P = 0.026) was observed for the inhibition of lipid peroxidation by unfermented Cyclopia spp. with the flavonol/flavone content. Antimutagenicity of Cyclopia spp. correlated weakly (r = 0.363, P = 0.012) with its hesperidin content. Antimutagenic activity of rooibos tea correlated moderately (r = 0.751, P < 0.005) with its flavonol/flavone content and specifically the flavones orientin (r = 0.674, P < 0.023) and iso-orientin (r = 0.728, P < 0.011). A strong negative correlation (r = -0.918, P < 0.0001) of antimutagenicity of rooibos with its aspalathin content was observed. Antimutagenic activity of Camellia sinensis teas did not correlate with their total polyphenol, flavanol or flavonol/flavone contents. The flavanol content of green tea showed a good, but marginal (P < 0.1) correlation (r = 0.824, P = 0.086) with decreased cytochrome P450 stability. The modulation of aniline-induced Type II binding to microsomal cytochrome P450 by green tea differed significantly (P < 0.05) from the modulation exhibited by rooibos and Cyclopia spp. Flavonoid glycosylation appeared to influence antimutagenic activity, stabilising of cytochrome P450 and modulation of substrate binding of selected phenolic compounds. The present study indicates that rooibos and Cyclopia spp. have in vitro antimutagenic activity against AFB1, suggesting that consumption of these two herbal teas may have beneficial health effects. It is also suggested that stabilising of cytochrome P450 by tea, and interaction of tea constituents with cytochrome P450, may influence their in vitro antimutagenic activity.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2005. / It is estimated by the World Health Organisation (WHO) that thousands of millions of cases of foodborne diseases occur world–wide every year. Enterobacter sakazakii is a member of the family Enterobacteriaceae and has been identified as an occasional contaminant of powdered infant formula milk (IFM). Enterobacter sakazakii is an opportunistic emerging pathogen and has the ability to cause a severe form of neonatal meningitis. This organism was referred to as “yellow pigmented Enterobacter cloacae” until 1980 after which it was renamed as E. sakazakii. The current method for the detection of E. sakazakii is very time consuming and includes pre–enrichment, enrichment in Enterobacteriaceae enrichment broth, subsequent plating on violet red bile glucose agar and subculturing on tryptone soy agar. In this study a polymerase chain reaction (PCR) method was developed for the identification of the presence of E. sakazakii in infant food products. A part of the 16S ribosomal RNA (rRNA) gene from E. sakazakii was amplified using the primer pair Esak2 and Esak3. An internal amplification control (IAC) was constructed as part of the PCR detection method. The 850 base pair (bp) E. sakazakii PCR product was digested with AluI and the two fragments containing the primer binding sites were ligated, resulting in a 240 bp IAC. During this study a positive band for both the target DNA (850 bp) and the IAC (240 bp) was simultaneously observed when the IAC was added to the PCR mixture at a concentration of 0.72 pg.ml-1. Four of 22 South African food products tested positive for the presence of E. sakazakii, using both the PCR and recommended culturing methods. The PCR method was used successfully for the detection of E. sakazakii within three days and thus provides a possible alternative and improvement on the recommended current culturing methods. Other microorganisms present in the products tested included Escherichia coli, Klebsiella pneumoniae, Raoultella terrigena (“Klebsiella terrigena”) and Chryseomonas luteola. Since E. sakazakii is usually present in low numbers in food products, it is possible that these few cells are unevenly distributed in the products, making it important to take multiple samples when evaluating IFM and thereby ensuring that even low numbers of this pathogen are detected.

Thesis (MSc Food Sc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The distillery industry produces large volumes of waste water with a high organic content throughout the year. These effluents must be treated in some manner before being discharged or recycled in the factory. Several treatment options are in use presently, but they all have disadvantages of some nature, such as long retention times, bad odours or the need for large areas of land. Considerable interest has been shown in the application of anaerobic digestion, especially the UASB design (upflow anaerobic sludge blanket), to treat this high strength waste water. Thus, the aim of this study was to investigate the efficiency of an upflow anaerobic sludge blanket (UASB) bioreactor using full-strength distillery effluent. The activity of the bacteria in the biogranules was also evaluated by developing an easy and reliable activity method to estimate the general biogas and methanogenic activity and to calibrate this method using different anaerobic granules from different sources. The influence of high strength distillery effluent on the anaerobic digestion process was investigated using a mesophilic lab-scale UASB bioreactor. During the experimental study, the organic loading rate (OLR) was gradually increased from 2.01 to 30.00 kgCOD.m-3.d-1, and simultaneously, the substrate pH was gradually lowered from 7.0 to 4.7. It was found that at an OLR of 30.00 kgCOD. m-3.d-1,the pH, alkalinity and biogas production stabilised to average values of 7.8, 6 000 mg.l-1 and 18.5 I.d-1 respectively. An average COD removal> 90% was found indicating excellent bioreactor stability. The low substrate pH holds considerable implications in terms of operational costs, as neutralisation of the biorector substrate is no longer necessary. The accumulation of fine solids present in the distillery substrate was found at the higher OLR's and resulted in the granular bed increasing with subsequent biomass washout and a lowering in efficiency parameters. However, a possible pre-treatment filtration of these fine solids would eliminate this problem. The success of the upflow anaerobic sludge bed (UASB) process is mainly due to the capability of retaining the active biomass in the reactor. Over the years, several methods have been developed to characterise and quantify sludge activity but each has advantages and disadvantages. There is thus an increasing need for a rapid method to evaluate the activity of the granular biomass. The activity method of Owen et al. (1979) as adapted by Lamb (1995), was thus evaluated in terms of efficiency and applicability in determining the activity of granular samples. The method was found to be inaccurate as well as time consuming and it was thus modified. Results obtained with the modified assay method were found to be more accurate and the impact of the different test substrates (glucose, lactate, acetate and formate) on activity, was more evident. The activity of seven different anaerobic granules, was subsequently evaluated. Biogas (Ss) and methanogenic (SM) activity was not measured in volume of gas produced per unit COD converted or volatile suspended solids (VSS), but as tempo of gas production (ml.h-1) in a standardised basic growth medium. The activity data obtained were also displayed as bar charts and "calibration scales". This illustrative depiction of activity data gave valuable information about population dynamics as well as possible substrate inhibition. The "calibration scales" can also be used to group the general biogas (Ss) and methanogenic activities (SM) of any new biogranule relative to active (O-type) and inactive (W-type) anaerobic granules, providing that the same method of activity testing is used. The "calibration scales" can thus be used to give a fast indication of how the activity value of one sample relates to the activity values of other granules, even when using different test substrates. / AFRIKAANSE OPSOMMING: Die stokery industrie produseer groot hoeveelhede afvalwater, wat hoë ladings van organiese materiaal gedurede die hele jaar bevat. Hierdie afvalwater moet op een of ander manier behandel word voordat dit gestort of vir hergebruik aangewend kan word. Daar is tans verskeie behandelingsmetodes wat gebruik kan word, maar elk het sy eie tekortkominge soos bv. lang retensie tye, onaangename reuke of die behoefte aan groot stukke oop grond. Groot belangstelling is getoon vir die gebruik van anaerobiese vertering, en meer spesifiek die "uflow anaerobic sludge blanket" UASB bioreaktor vir die behandeling van stokery uitvloeisels. Die doel van die studie was dus om die algehele effektiwiteit van 'n UASB bioreaktor, wat onverdunde stokery uitvloeisel behandel, te evalueer. Die methanogene- en algehele aktiwiteit van die bakterië in die biogranules was ook ge-evalueer deurdat 'n maklike en betroubare aktiwiteitsmetode omtwikkel is, waarna hierdie metode ook toegepas was op 'n reeks van verskillende tipe biogranules. Die invloed van volsterkte stokery uitvloeisel op die anaerobiese verteringsprosesse was ondersoek met die gebruik van 'n mesofiele laboratoriumskaal UASB bioreaktor. Gedurende die eksperimentele studie, was die organiese ladingstempo (OLT) verhoog van 2.01 na 30.00 kgCSB.m-3.d-1 (CSB = chemiese suurstof behoefte) met die gelyktydige verlaging in die pH van die bioreaktorsubstraat van 7.0 na 4.7. Dit was vasgestel dat met 'n OLT van 30.00 kgCSB.m-3.d-1, die pH, alkaliniteit en biogas geproduseer, gestabiliseer het na gemiddelde waardes van 7.8, 6000 mg.-1 en 18.5l.d-1 , respektiewelik, sowel as 'n gemiddelde CSB verwydering van> 90%. Al hierdie waardes dui uitstekende bioreaktor stabiliteit aan. Die lae bioreaktorsubstraat pH kan van groot waarde wees vir die industrie, aangesien neutralisering van die uitvloeisel nie meer nodig is nie en kan sodoende die operasionele koste van die proses verlaag. Die konsentrering van fyn opgeloste soliedes in die bioreaktor by hoë OLT's, kan egter problematies raak, aangesien dit die granule-bed kan vergroot en veroorsaak dat van die biomassa uitspoel en kan verlore gaan. Die verlies van aktiewe biomassa kan die effektiwiteitsparameters negatief beinvloed, maar die plasing van 'n filterings stap voor die verterings stap, behoort hierdie probleem op te los. The sukses van die UASB-stelsel rus op die versekering dat die aktiewe biomassa in die reaktor behoue bly. Oor die jare was daar 'n verskeidenheid van aktiwiteitstoetsings-metodes ontwikkel, elk met sy eie nadele. Daar bestaan dus nog steeds 'n groot behoefte vir die daarstelling van 'n aktiwiteitstoetsings-metode wat vinnig en maklik is om uittevoer. Die aktiwiteitstoetsings-metode van Owen et al. (1979) wat deur Lamb (1995) aangepas is, was in terme van sy effektiwiteit en toepaslikheid ten opsigte van die gebruik daarvan vir aktiwiteitstoetsing vir biogranules, ge-evalueer. Dit is bevind dat die metode onakkuraat sowel as tydsrowend was en gevolglik dus aangepas. Die aangepaste metode het meer akkurate resultate gelewer en die impak van die verskillende toetssubstrate (glukose, laktaat, asetaat en formaat) op die granules het ook meer duidelik na vore gekom. Gevolglik was die aktiwiteit van sewe verskillende anaerobiese biogranules ondersoek. Die eenheid waarin atiwiteitsresultate aangegee is, was nie in volume gas geproduseer per eenheid CSB verwyder of per hoeveelheid gesuspendeerde vlugtige vetsure in die biomassa nie, maar as tempo van biogas (S8)- of metaan (SM)produksie (ml.h-1). Die data wat op hierdie wyse bekom was, is gebruik om staafdiagramme sowel as "kalibrasie skale" daar te stel. Hierdie illustrerende wyse om aktiwiteitsdata uit te beeld verskaf waardevolle informasie ten opsigte van die interaksies tussen die verskillende populasies in die granule en kan ook die aanwesigheid van moontlike substraat inhibisie aandui. Die "Kalibrasie skale" kan ook gebruik word om die algehele (SB) en methanogene (SM)aktiwiteite van einge nuwe biogranule vinnig te klassifiseer ten op sigte van 'n aktiewe (O-tipe) en 'n minder aktiewe (W-tipe) anaerobiese granules, mits dieselfde metode gebruik word om die aktiwiteits data te bekom.

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The "classical" propionibacteria are used in a variety of natural dairy fermentations where they produce natural preservatives (propionic and acetic acids and bacteriocins) and large amounts of vitamin B12. The extracellular polysaccharide (ECP) producing ability of these bacteria also make them of special interest to the food and waste water management industries as the ECP has been illustrated to playa role in the initial granule formation in upflow anaerobic bioreactor systems. There is little known on the ECP production by propionibacteria and in this study different environmental conditions that influence ECP production were studied. Nineteen different Propionibacterium strains were examined in terms of ECP production and Propionibacterium strain 278 was identified as the best ECP producer. Further studies were only done on this strain because of its high ECP production and because it was originally isolated from an anaerobic digester. The influence of temperature, pH and sucrose concentration was determined through the measurement of ECP production and medium viscosity. It was found that more ECP was produced at temperatures lower than the optimum for growth with the optimum being between 22° and 25°C. Lower initial pH conditions of the growth medium (below pH 7.0) were found to inhibit ECP production and the influence when the initial pH values were between 7.0 and 8.5, was not significant. A higher carbon: nitrogen ratio, when 8% sucrose was added, was also found to enhance the ECP production. The upflow anaerobic sludge bed (UASB) bioreactor process depends on the upward movement of soluble matter through a blanket of active methanogenic granular sludge. The long start-up times as a result of the slow granulation process, as well as the need for a speedy replacement of granules once they have been washed out of the system, are limitations that restrict the general application of this excellent waste water treatment technology. Full exploitation of this biomass immobilisation technique can thus not be realised until the granule formation conditions are defined and optimised. The precise nature of the mechanisms involved in the formation of granules and the reason for their stability, is still not fully understood. It was hypothised by Britz et al. in 1999 that, through the implementation of environmental 'stress' conditions, a shift in the population dynamics of the anaerobic community can be obtained. This results in a concurrent increase in ECP formation that appears to enhance aggregate formation. In the second study it was found that, when 'stress' conditions were applied to already formed granules, the Gram-positive lactate-utilising acidogenic population gained an advantage and more propionic acid producing bacteria were present. The propionic and acetic acid concentrations were also found to increase, and concurrently, a decrease in the growth medium pH occurred. This confirms part of the granulation hypothesis that, when granules are 'stressed', the acidogenic population dynamics change and the lactate-utilising population responds to the gradual decrease in pH and the more acid-tolerant propionic acid producing bacteria gain a competitive advantage resulting in the increase in the propionic acid concentration. When propionibacteria were added to raw sludge during the granule production process, the granules were found to be more active than when nopropionibacteria had been added. This was probably due to the ECP formation by the propionibacteria that enhances the aggregation of the granules. Enhanced granulation was thus found in the batch systems with the fatty acids formed in correlation with the model for granulation. A good correlation was evident between the hypothesis and the experimental data and the hypothesis was partially verified in this study. / AFRIKAANSE OPSOMMING: Die "klassieke" propionibakterieë word in 'n verskeidenheid van natuurlike suiwel fermantasies gebruik waarin hulle verantwoordelik in vir die produksie van natuurlike voedsel preserveermiddels (propioonsuur, asynsuur en bakteriosiene) en groot hoeveelhede vitamiene B12. Die Ekstra Sellulêre Pollisakkaried (ESP) produserende eienskap van hierdie groep bakterieë maak hulle ook van belang in die voedsel en afvoerwater beheer industrieë, aangesien gevind is dat ESP 'n rol speel in die aanvanklike granule formasie in anaerobiese bioreaktor sisteme. Daar is nog baie min bekend oor die ESP produksie van propionibakterieë en in hierdie studie is verskeie omgewings faktore wat die ESP produksie beïnvloed, bestudeer. Negentien verskillende Propionibakterium stamme was bestudeer in terme van ESP produksie en Propionibakterium stam 278 was geïdentifiseer as die stam wat die meeste ESP produseer. Verdere studies was op hierdie stam gedoen na aanleiding van sy hoë ESP produksie en omdat dit oorspronklik uit 'n anaerobiese verteerder geisoleer is. Die invloed van termperatuur, pH en sukrose konsentrasie was bepaal deur die meting van die ESP produksie en die medium viskositeit. Dit was gevind dat meer ESP geproduseer was by temperature laer as die optimum vir groei, met die optimum temperatuur tussen 22° en 25°C. Dit is ook gevind dat laer aanvangs groei-medium pH (laer as pH 7.0), ESP produksie inhibeer. Die invloed van die aanvangs groei-medium pH tussen 7.0 en 8.5 was egter nie betekenisvol nie. Dit is ook gevind dat 'n hoër koolstof tot stikstof verhouding, verkry deur die byvoeging van 8% sukrose, die ESP produksie verhoog. Die "upflow anaerobic sludge blanket" (UASB) proses vind plaas as gevolg van die opwaarste beweging van opgeloste organiese materiaal deur 'n granule bed van aktiewe metanogeniese granulêre slyk. Die lang 'start-up' tye as gevolg van die stadige granulasie proses, en die nodigheid om 'n vinnige verplasing van granules te hê nadat dit uit die sisteem gewas is, is beperkings wat die algemene toepassing van hierdie fantastiese afvoerwater tegnologie, strem. Volle implementering van hierdie biomassa immobilisereings tegniek kan dus nie plaasvind voordat die granule formasie gedefinieer en geoptimiseer is nie. Die presiese eienskappe van die meganismes betrokke en die formasie van die granules en die rede vir hul stabiliteit word egter nog nie ten volle verstaan nie. Volgens 'n hipotese deur Britz et al. (1999), vind 'n verskuiwing in die populasie dinamika van die anaerobiese gemeenskap plaas tydens die implementasie van omgewings 'stress' toestande. Die resultaat is 'n verhoging in ESP produksie en 'n gevolglike verbetering in die granulasie proses. In die tweede studie was dit gevind dat, wanneer 'stress' toestande op die reeds gevormde granulasie toegepas word, die Gram-positiewe laktaat-benuttende asetogeniese populasie voordeel geniet en meer propioonsuur produserende bakterieë was teenwoordig. Die propioonsuur en asynsuur konsentrasies het ook verhoog en met 'n gevolglike daling in die groei-medium se pH. Dit bevestig 'n gedeelte van die hipotese dat, wanneer die granules onder 'stress' geplaas word, die asetogeniese populasie dinamika verander en die laktaat-benuttende populasie reageer tot die gedeeltelike afname in pH. Die meer suur-tolerante propioonsuur produserende bakterieë verkry 'n kompeterende voordeel en gevolglik is daar 'n verhoging in propioonsuur konsentrasie. Propionibakterieë was gevoeg by die onbehandelde slyk gedurende die granule produksie proses, en daar is gevind dat meer aktiewe granules gevorm word as andersins. Dit is moontlik as gevolg van die die ESP produksie van propionibakterieë wat die granulasie versnel het. Verbeterde granulasie was dus verkry in die sisteme waar propionibakterieë bygevoeg is. Vetsuur analises het gedui dat die gevormde vetsure ook in korrelasie was met die model van granulasie. Goeie korrelasie was dus verkry tussen die hipotese en die eksperimentele data en die hipotese is gedeeltelik bewys in hierdie studie.

Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The potential use of the upflow anaerobic sludge blanket (UASB) bioreactor is limited by the extended start-up periods due to the time-consuming granulation process and the fact that seeding inoculum is not freely available in most developing countries like South Africa. The mass cultivation of granules would provide the waste water treatment industry with suitable seeding inoculum and, therefore, an efficient waste water treatment option would be more easily available. By applying 'stress' conditions on a bioreactor system seeded with raw anaerobic sludge, the population dynamics of the anaerobic community change and the acidogens start to produce extracellular polymers, which in turn enhance the granulation process by providing a matrix for the bacterial cells to adhere to. These "environmental stress" conditions include changes in the C:P:N ratio's. The aim of this study was, therefore, to assess the impact of different carbon and nitrogen sources on the enhancement of granulation in a batch system, and to determine the best preservation technique in terms of retainment of activity. It was found that the carbon source and concentration had a significant influence on batch granule enhancement. Low concentrations (2.g.l ̄ ¹) of glucose gave the best granule enhancement over a 14 day incubation period. Fruit cocktail effluent was found to be a cheap and effective carbon source for batch granule cultivation. It was found that different nitrogen sources did not have the same impact on granule enhancement, however, urea, at all concentrations tested, gave the best granule enhancement. A major problem encountered during the study was the standardisation of the inoculum. Significant granule enhancement comparisons between the different carbon sources were impeded by the lack of a suitable and reliable form of sludge standardisation. Future research needs to address this problem of the standardisation of the sludge inoculum as this would lead to more kinetically comparable results. Mass granule culturing will require granule preservation without risking the loss of activity. In the second study, six different preservation techniques and storage periods were evaluated in terms of the retainment of activity. These involved freeze-drying, vacuum freeze-drying, vacuum-drying, freezing, cold storage and room temperature preservation. Activity testing was used for comparing the efficiency of the different preservation techniques in terms of the tempo of biogas and methane production. Freeze-drying the granules, with storage for up to 90 days was found to give the best retainment of activity, followed by vacuum freeze-drying. The room temperature preserved samples showed a sudden increase in activity by day 120, which could possibly be explained by cell hydrolysis of the granules after day 90. The highest activity was achieved after 10 h of incubation, and it was, therefore, suggested that activity testing for evaluation purposes should use an incubation time of only 10 h. Furthermore, only the basic test medium with added glucose should be used for activity testing as it was observed that the addition of lactate and acetic acid played no decisive role in determining the level of activity of the granules. This study recommends the use of low concentrations of glucose for optimum granule enhancement during the mass cultivation of granules, and the addition of low concentrations of lactate to ensure a stable system with no acidification. It is also advisable to use a standardised sludge inoculum, as this will allow more efficient comparisons. Freeze-drying is recommended as preservationtechnique as this technique showed the best retainment of activity. A storage period of 90 days is, however, too short to be of much use for the industry. This will have to be investigated, together with the phenomenon of increased activity after 90 days as shown by the room temperature preserved granules. / AFRIKAANSE OPSOMMING: Die potensiële gebruik van die "uptflow anaerobic sludge blanket" (UASB) bioreaktor word beperk deur verlengde aansitprosedure as gevolg van die tydsame granulasieproses en die feit dat geskikte inokulums nie vrylik beskikbaar is in die meeste ontwikkelende lande, bv. Suid-Afrika nie. Die massa-kweking van granules sal die afvalwater-industrie voorsien van 'n geskikte inokulum, en sodoende 'n effektiewe opsie vir die behandeling van afvalwater beskikbaar stel. Deur die aanwending van "stres" toestande op 'n reaktor, wat geinokuleer is met rou anaerobe slyk, vind daar 'n verandering in die samestelling van die anaerobe populasie plaas. Die laktaat-benuttende asidogene begin om ekstrasellulêre polisakkariede te produseer wat die granulasieproses versnel deur 'n matriks te voorsien waaraan die bakteriële selle kan heg. Hierdie "omgewings stres" toestande sluit veranderinge in die C:P:N verhoudings in. Die doel van hierdie studie was om die invloed van verskillende koolstof- en stikstofbronne op die vermeerdering van granules te bepaal, asook om die beste preserveringstegniek in terme van die behoud van aktiwiteit te bepaal. Daar is gevind dat die koolstofbron en konsentrasie 'n betekenisvolle invloed op granule-vermeerdering het. Lae konsentrasies glukose (2 g.I ̄ ¹) het tot die grootste vermeerdering in granules oor 'n 14 dae inkubasieperiode gelei. Vrugtekelkie-afvalwater is geidentifiseer as 'n goedkoop en effektiewe koolstofbron wat ook gebruik kan word vir die kweking van granules. Voorts is gevind dat die stikstofbron en konsentrasie nie so 'n groot invloed op granule-vermeerdering het nie. Urea het nietemin die beste granule-vermeerdering vir al die konsentrasies wat getoets is, gegee. Standaardisasie van die inokulum was 'n groot probleem gedurende die studie. Betekenisvolle vergelykings tussen die granule-vermeerderings verkry met die verskeie groeimedia is bemoeilik deur die afwesigheid van 'n geskikte en betroubare standaardisasie-metode. Toekomstige navorsing moet hierdie probleem aanspreek aangesien dit sal lei tot meer kineties vergelykbare resultate. Massa-kweking van granule sal 'n metode van granule-preservering vereis sonder enige verlies van aktiwiteit. In die tweede studie is ses verskillende preserverings-tegnieke en opbergings-periodes in terme van die behoud van aktiwiteit geëvalueer. Die tegnieke sluit in: vriesdroging; vakuum-vriesdroging; vakuumdroging; bevriesing; koelopberging en kamertemperatuur-preservering. Aktiwiteitstoetsing is gebruik vir die vergelyking van die effektiwiteit tussen die verskillende preserverings-tegnieke in terme van die tempo van biogas- en metaanproduksie. Die granules wat met behulp van die vriesdroogtegniek gepreserveer is, het die beste behoud van aktiwiteit getoon, gevolg deur die vakuum-gevriesdroogde granules. Die monsters wat by kamertemperatuur gepreserveer is, het 'n skielike toename in aktiwiteit na 120 dae van opberging getoon en 'n moontlike verklaring vir hierdie verskynsel kan sel-hidrolise van die granules na 90 dae van opberging wees. Die meeste aktiwiteit is behaal na 'n 10 h inkubasietyd, en dus word hierdie inkubasietyd aanbeveel indien aktiwiteitstoetse vir evaluerings-doeleindes gedoen word. Verder word aanbeveel dat slegs die glukose-verrykte basiese toetsmedia vir aktiwiteitstoetsing gebruik word aangesien die byvoeging van laktaat en asynsuur geen noemenswaardige rol speel in die bepaling van die vlak van aktiwiteit van die granules nie. Hierdie studie beveel die gebruik van lae glukosekonsentrasies aan vir optimale vermeerdering van granules tydens die massakweking daarvan, asook die byvoeging van lae konsentrasies laktaat om 'n stabiele sisteem met geen versuring te verseker. Die gebruik van 'n gestandaardiseerde slyk-inokulum word sterk aanbeveel aangesien dit meer vergelykbare resultate lewer. Vriesdroging (as preserveringstegniek) het die beste behoud van aktiwiteit in die granules getoon en word dus as preserveringstegniek aanbeveel. 'n Opbergingsperiode van 90 dae is egter te kort om van veel waarde vir die industrie te wees. Hierdie probleem, asook die verskynsel van 'n verhoging in aktiwiteit na 90 dae van die granules wat by kamertemperatuur gepreserveer is, moet verder ondersoek word.

Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The rapid urbanisation of the African population has led to the establishment of large low-income communities in and around almost every major town and city in South Africa. Several factors prevent these people from producing or obtaining their traditional fermented milk drink, Maas (Amasi), often resulting in the occurrence of malnutrition in low-income urban African communities. A product with the potential to satisfy the demand for a fermented milk product is Kefir. Kefir, a self-carbonated fermented milk, is commonly manufactured by fermenting unpasteurised or pasteurised milk with re-usable Kefir grains. These Kefir grains consist of a combination of mainly lactic acid bacteria and yeasts. Neither Kefir, nor Kefir grains are as yet marketed in South Africa, thus creating an excellent opportunity to launch these products locally. It is often difficult for the low-income communities to obtain high quality unpasteurised or pasteurised milk, resulting in a serious health risk. The inhibitory activity of Kefir towards certain spoilage and pathogenic microorganisms was, therefore, studied. Strains of Escherichia coli, Staphylococcus aureus, Bacillus cereus, Usteria monocytogenes and Clostridium tyrobutyricum were inoculated (10 ³ - 10 ⁴ cfu.ml⁻¹ ) into pasteurised milk together with Kefir grains (18 gram per litre) and incubated at 25°C. Uninoculated milk samples and milk samples inoculated only with test organisms served as controls. Growth of all the test organisms were inhibited substantially (>-99.9%) in Kefir over the 30 h incubation period and substantial reductions in microbial log cycles were observed for many of the organisms. This coincided with a steep decrease in pH (6.57 - 4.06) and increase in titratabie acidity (0.20 - 0.72%). If Kefir is eventually marketed to low-income urban African consumers, it will have to compete with Maas and, therefore, comparative sensory testing of Kefir and Maas was conducted. The differences in the sensory properties of Kefir, 'laboratory' Maas (representing traditional Maas) and commercial Maas (containing thickener, colourants and flavourants) were determined by a trained panel. These characteristics were identified as "yeasty" and "cowy" tastes (p < 0.05), "effervescence" (p < 0.01), as well as "sourness," "creaminess" and "smoothness" (p < 0.001). The effect of different incubation temperatures (25°, 30° and 35°C) on the Kefir sensory properties was studied to simulate the effect of the large temperature variations that would be found in the dwellings of low-income African urbanites. The "sourness" and "creaminess" of the Kefir was found to increase with increase in incubation temperature but no strong off-flavours were found to develop. Sensory preference testing was conducted by consumer panels consisting of panellists of different ages and population groups to indicate whether the specific panels significantly prefer Kefir, commercial Maas or laboratory Maas. It was found that commercial Maas was significantly (p < 0.001) preferred to Kefir by young African urbanites. Adult Africans, who presumably still have traditional taste preferences, however, equally (p > 0.05) preferred Kefir and laboratory Maas, identifying this segment of the African population as the appropriate starting target market for Kefir. Kefir and laboratory Maas were also tested for preference by a wider panel consisting of people (aged between 18 and 25) representing the different population groups in South Africa. Kefir and laboratory Maas were preferred equally (p > 0.05) by all the groups. Several arguments supporting Kefir marketing to the low-income urban African population of South Africa have been identified. These include: Kefir's ease of preparation; the re-usability of Kefir grains and subsequent affordability; good packaging, distribution and storage possibilities; Kefir's acceptability by lactoseintolerant individuals; high nutritional value; the inhibitory activity of Kefir against potential spoilage and pathogenic organisms and subsequent enhanced safety and keeping ability; and Kefir's acceptable refreshing taste. / AFRIKAANSE OPSOMMING: Die toenemende verstedeliking van Swart Suid-Afrikaners het gelei tot die vestiging van groot lae-inkomste gemeenskappe in en om die meeste groot dorpe en stede. Verskeie faktore verhoed dat hierdie gemeenskappe hul tradisionele gefermenteerde melk, naamlik Maas (Amasi), self kan maak of koop. Dit lei dikwels tot wanvoeding onder lae-inkomste stedelike Swart verbruikers. Kefir het die potensiaal om te voorsien in die vraag na 'n gefermenteerde melk produk in lae inkomste stedelike Swart gemeenskappe. Kefir is 'n selfgekarboneerde, gefermenteerde melk wat vervaarding word deur die fermentasie van ongepasteuriseerde of gepasteuriseerde melk met herbruikbare Kefirkorrels. Hierdie Kefirkorrels bestaan uit 'n kombinasie van hoofsaaklik melksuurbakterieë en giste. Kefir en Kefirkorrels word glad nie in Suid-Afrika bemark nie, en bied 'n fantastiese geleentheid om hierdie produkte plaaslik bekend te stel. Dit is dikwels moeilik om hoë kwaliteit ongepasteuriseerde of gepasteuriseerde melk in lae-inkomste gemeenskappe te verkry. Die risiko om siektes deur die verbruik van hierdie melk op te doen, bestaan dus. Om hierdie rede is die inhiberende effek van Kefir teenoor spesifieke bederf- en patogeniese bakterieë bestudeer. Rasse van Escherichia coli, Staphylococcus aureus, Bacillus cereus, Usteria monocytogenes en Clostridium tyrobutyricum is geïnokuleer (10 ³ - 10 ⁴ cfu.ml⁻¹) in gepasteuriseerde melk tesame met Kefirkorrels (18 gram per liter) en geïnkubeer by 25°C. Melkmonsters wat slegs geïnokuleer is met die toetsorganismes het as kontroles gedien. Die groei van al die toetsorganismes is substansieël geïnhibeer (>-99.9%) in Kefir gedurende die 30 h inkubasieperiode. Substansiële afnames in logsiklusgetalle is waargeneem vir baie van die organismes. Dit het gepaard gegaan met 'n skerp afname in pH (6.57 - 4.06) en toename in titreerbare suurheid (0.20 - 0.72%) vir die Kefirmonsters gedurende die 30 h inkubasieperiode. lndien Kefir bemark word aan lae-inkomste stedelike Swart verbruikers sal dit moet kompeteer met Maas. Vergelykende sensoriese toetse is dus uitgevoer. Die verskille in die sensoriese eienskappe van Kefir, 'laboratorium' Maas (verteenwoordigend van tradisionele Maas) en kommersiële Maas (wat verdikker, kleur- en geurmiddels bevat) is bepaal deur 'n opgeleide paneel en geïdentifiseer as die" "gis-" en "koeismake" (p < 0.05), die "gasserigheid" (p < 0.01) asook die "suurheid", "romerigheid" en "gladheid" (p < 0.001) van die monsters. Die effek van verskillende inkubasietemperature (25°, 30° en 35°C) op die sensoriese eienskappe van Kefir is bestudeer om die effek van die groot temperatuurvariasies wat in laeinkomste behuising mag voorkom, te simuleer. Daar is bevind dat die "suurheid" en "romerigheid" van Kefir toeneem met verhoging in inkubasietemperatuur terwyl geen afsmake ontwikkel nie. Sensoriese voorkeurtoetse is deur verbruikerspanele van verskillende ouderdomme en bevolkingsgroepe uitgevoer om te bepaal of die spesifieke panele 'n beduidende voorkeur toon vir Kefir, laboratorium Maas of kommersiële Maas. Daar is bevind dat stedelike Swart jongmense kommersiële Maas beduidend (p < 0.001) bo Kefir verkies. Swart volwassenes met verwagte tradisionele smaakvoorkeure het egter Kefir en laboratorium Maas ewe veel verkies (p > 0.05). Hierdie segment van die Swart bevolking is dus die geskikte teikenmark vir die bekendstelling van Kefir. Voorkeur vir Kefir en laboratorium Maas is ook getoets deur 'n paneel (ouderdom 18 - 25 jaar) wat bestaan uit mense van verskillende bevolkingsgroepe. AI die groepe het Kefir en Maas ewe veel verkies (p > 0.05). Verskeie argumente ten gunste van die bemarking van Kefir aan lae-inkomste stedelike Swart gemeenskappe in Suid-Afrika is geïdentifiseer. Dit behels die volgende: die gerief van Kefirvervaardiging; die herbruikbaarheid van Kefirkorrels en gevolglike bekostigbaarheid; goeie verpakkings-, verspreidings- en opbergingsmoontlikhede; Kefir se aanvaarbaarheid vir laktose-intolerante individue; Kefir se hoë voedingswaarde; die inhiberende aktiwiteit wat Kefir teenoor potensiële bederf- en patogeniese organismes het en die gevolglike verhoging in veiligheid en rakleeftyd van melk; en Kefir se aanvaarbare verfrissende smaak.

Thesis (MSc Food Sc )--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The focus of this study was the development of food products produced from the neck flesh of Cape hake (Merluccius capensis) as a means of adding value to hake heads. The product prototypes that have been developed include curried fish chowder (packaged in stand-up pouches), fish spread (packaged in plastic casings) and Chakalaka hake (packaged in both cans and retortabie pouches). A formula for fish stock, which was used as a base ingredient in the three product prototypes, has also been standardised. Shelf life testing was regarded an essential part of the development processes for the refrigerated product prototypes i.e. the curried fish chowder and the fish spread. Shelf life determinations involved microbiological testing based on set microbiological standards as well as sensory monitoring and pH testing. Proximate chemical- and mineral analyses were performed on freeze-dried samples of the developed product prototypes. The efficiency of the antimicrobial peptides enterocin 1071 A and 1071 B, as biological preservatives, versus that of conventional artificial preservatives was evaluated in the fish spread prototype. Three batches of fish spread were prepared: one containing the enterocin crude extract; the second a combination of sodium benzoate and potassium sorbate, while the third batch containing no preservatives served as the control. Microbiological- and histamine tests coupled with organoleptic monitoring and pH testing were carried out over a 21-day period. It was concluded that although enterocins 1071A and 1071B had some preserving effect in the fish spread, the artificial preservative combination was the superior preserving agent. However, neither the biological preservatives nor the artificial preservative combination succeeded in providing a satisfactory shelf life. The preserving agents used in this study were however not necessarily included at optimum levels and higher levels could possibly lead to an improved shelf life. The influence of two processing temperatures [121°C (249.8°F) and 116°C (240.8°F)] and two food container types (retortable pouch and can) on the sensory quality characteristics of the Chakalaka hake-prototype was investigated. The results indicated that the shorter processing time obtained with a higher processing temperature resulted in a product of better sensory quality. The sensory quality characteristics of Chakalaka hake processed in cans at 121°C were closest to that considered desirable for the product. / AFRIKAANSE OPSOMMING: Die fokus van hierdie studie was die ontwikkeling van voedselprodukte geproduseer uit die nekvleis van stokvis (Merluccius capensis) met die doeI om waarde by stokviskoppe te voeg. Die volgende produk-prototipes is ontwikkel: 'n dik vissop met 'n kerriegeur (verpak in regopstaande sakkies), 'n vissmeer (verpak in plastiekomhulsels) en Chakalaka hake (verpak beide in blikkies en retortbestande sakkies). 'n Formule vir visaftreksel, wat as 'n basis-bestanddeel in die drie produk-prototipes gebruik is, is ook gestandaardiseer. Rakleeftydstudies het 'n belangrike deel van die ontwikkelingsprosesse van die verkoelde produk-prototipes, d.i. die dik vissop en die vissmeer, uitgemaak, Rakleeftydbepalings het mikrobiologiese toetsing, gebaseer op vasgestelde mikrobiologiese standaarde, sowel as die monitor van sensoriese eienskappe en pH metings behels. Proksimale chemiese- en mineraal analises is uitgevoer op gevriesdroogde monsters van die ontwikkelde produk-prototipes. Die effektiwiteit van die antimikrobiese peptiede enterosien 1071 A en 1071 B, as biologiese preserveermiddels, is ondersoek in vergelyking met dit van konvensionele kunsmatige preserveermiddels in die vissmeer-prototipe. Drie mengsels vissmeer is berei waarvan die eerste enterosien kru-ekstrak bevat het; die tweede 'n kombinasie van natrium bensoaat en kalium sorbaat, terwyl 'n derde mengsel geen preserveermiddels bevat het nie en gedien het as kontrole. Mikrobiologiese- en histamien toetse is gelyklopend met organoleptiese monitering en pH metings oor 'n tydperk van 21 dae op monsters van die drie vissmeermengsels uitgevoer. Die ondersoek het getoon dat enterosien 1071 A en 1071 B wel 'n mate van bederfwering in die vissmeer meegebring het, maar dat die kunsmatige preserveermiddelkombinasie 'n beter preserveringseffek gehad het in die produk. Nie die biologiese preserveermiddels óf die kunsmatige preserveermiddelkombinasie kon 'n bevredigende rakleeftyd teweegbring nie. Die preserveermiddels in hierdie studie is egter nie noodwendig in optimale hoeveelhede gebruik nie en hoër vlakke kan moontlik tot 'n verbeterde rakleeftyd lei. Die effek van twee prosesseringstemperature [121 °C (249.8°F) en 116°C (240.8°F)], sowel as twee verpakkingstipes (retortbestande sakkie en blik), op die sensoriese kwaliteitseienskappe van die 'Chakalaka hake' -prototipe is ondersoek. Die resultate het aangedui dat die korter prosesseringstyd verkry met 'n hoër prosesseringstemperatuur, gelei het tot 'n produk van beter sensoriese gehalte. Die sensoriese kwaliteitseienskappe van 'Chakalaka hake' geprosesseer in blikke by 121°C was die naaste aan dit wat beskou word as gewens vir die produk.