Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2007. / Distilleries are an example of an agricultural industry that generates large volumes of wastewater. These wastewaters are heavily polluted, and due to the seasonal nature of the product, the amount and composition of the wastewater may exhibit major daily and seasonal variations. Wine-distillery wastewaters (WDWWs) typically are acidic (pH 3.5 - 5.0) and have a high organic content (sugars, alcohol, proteins, carbohydrates and lipids), a COD range of 10 000 – 60 000 mg.L-1, have a high suspended solids content as well as containing various inorganic compounds. Additionally refractory compounds present in these wastewaters, such as polyphenols, can be toxic for biological processes, making the selection of a suitable treatment process problematic. Wetlands have been shown to be a feasible treatment for effluent originating from wine, however, they are normally used as a secondary treatment method and not well suited for high volume, high COD (> 5 000 mg.L-1) wastewaters. Ozone has been successfully used as a pre-treatment for WDWW due to its oxidising capabilities to partially biodegrade organics and non-biodegradable organics, and reduce polyphenols, which results in an increase in biodegradability. Currently a wetland system is being used on its own at a distillery to treat wastewater from a series of stabilisation dams, but the legal requirement for discharge into a natural resource (COD < 75 mg.L-1) is not being met. Additional treatments suited for WDWW are therefore being considered. Wine-distillery wastewater was characterised and found to show a large variation over time (COD ranging from 12 609 - 21 150 mg.L-1). Ozonation of WDWWs was found to be effective in decreasing COD over a wide range of organic loads. For pre-wetland wastewater from the distillery, an average COD reduction of 271 mg COD.g O3-1 was found, and for post-wetland effluent, an average of 103 mg COD.g O3-1. The effect of ozone on the biodegradability of the wastewater was monitored by activity tests, and a low ozone dose (200 - 400 mg O3.L-1) was found to increase activity in terms of biogas, methane and cumulative gas volumes. By showing an increase in the biodegradability of WDWW, it was concluded that ozone has potential as a pre-treatment step to increase the effectiveness of a biological wetland system. Lab-scale wetlands were used in trials to determine the effect of pre- and post-ozonation on WDWW. It was found that the efficiency of the wetland receiving the pre-ozonated “off-season” WDWW (2 200 mg COD.L-1) had a higher COD reduction (73%) than the wetland fed with untreated (62% COD reduction) WDWW, and the total polyphenol content was reduced by 40 and 31%, respectively. Treatment efficiency in terms of the reduction of colour, total solids, suspended solids and phosphates were also greatly improved for the pre-ozonated WDWW. Similar results were found when treating high COD “peak season” (7 000 mg COD.L-1) WDWW, with higher reduction rates for the wetland treating pre-ozonated WDWW (84% COD reduction) than for the wetland fed with untreated WDWW (74% COD reduction), and the total polyphenol content was reduced by 76 and 72%, respectively. Post-ozonation was also shown to be beneficial in that it improved the final effluent quality leaving the wetland system. Increasing the hydraulic retention time (HRT) of the wetlands from 9 days to 12 days resulted in similar COD reductions for the control and experimental wetland, highlighting the benefits that pre-ozonation has on reducing the acclimatisation period. Therefore using ozone as a pre-treatment could help in reducing the wetland size, HRT and allow increased volumes of wastewater to be treated. In this study ozone was successfully utilised to reduce COD levels in wine-distillery wastewater, and increase the biodegradability of the wastewater. This study also showed that ozone, used as a pre-treatment to a wetland system, can contribute to improving the performance of a wetland system in terms of higher removal efficiencies. Wetlands are, however, unsuited for treating high strength COD wastewater, and the final effluent was still well above the South African legal limit for direct discharge into a natural resource. The results obtained during this study contributed to developing a method to achieve a more efficient treatment system utilising wetlands for the distillery industry, and can be of value in facilitating efficient environmental management.

Thesis (Msc Food Sc (Food Science))--Stellenbosch University, 2008. / Extraction efficiency of soluble solids (SS), total polyphenols (TP) and xanthones (AlCl3 assay) from dried, green Cyclopia subternata, as affected by mass-solvent ratio, extraction time and solvents, was investigated. In addition the effect of solvent composition on extraction of mangiferin and hesperidin was determined. Extraction of 5 g plant material as opposed to 0.5 and 1 g resulted in lower recoveries of SS, TP and xanthones (P<0.05). Extraction of SS and TP increased during the initial 20 min of contact time, where after it remained constant (P>0.05). Water, 33% acetonitrile, ethanol (50, 80 and 100%), methanol (50 and 100%) and 70% acetone were investigated as extraction solvents. Extraction for 30 min with 33% acetonitrile on a steam bath or 50% ethanol at 64°C on a water bath proved to be the most effective for extraction of SS, TP and xanthones, while 33% acetonitrile was most effective in extracting hesperidin from C. subternata. However, 70% acetone was most effective in extracting mangiferin. A poor correlation (r = 0.54) was observed for the total antioxidant activity (TAA) of C. subternata, as determined for water extracts and with the mangiferin content determined by HPLC. A moderate correlation (r = 0.85) was, however, obtained for TAA and TP content. The mangiferin content of green C. subternata can be determined using the aluminium chloride (AlCl3) colorimetric method. A moderate correlation (r = 0.87) was found for the xanthone content of the plant material determined using the AlCl3 colorimetric method and mangiferin content quantified by HPLC (y = 1.2x + 0.54) following extraction with hot water. For extraction using 33% acetonitrile a weaker correlation (r = 0.74; y = 1.3x + 0.87) was found between the xanthone and mangiferin contents. The xanthone content (determined by AlCl3) of the plant material as extracted by the two solvents, correlated well (r = 0.91). Good correlations were also obtained, when comparing extractions with water and 33% acetonitrile, for determination of the SS (0.94) and mangiferin contents (r = 0.97) of the plant material. Near infrared (NIR) spectroscopy was investigated as a rapid and more economical method for prediction of mangiferin and xanthone contents of dried, green C. subternata plant material. NIR spectroscopy calibration models can be used for screening purposes for the mangiferin and (SEP = 0.21 g.100 g-1; r = 0.82) and xanthone (SEP = 0.27 g.100 g-1; r = 0.81) contents. The effect of various pre-drying treatments and storage temperatures on the colour, soluble SS, TP, mangiferin and hesperidin contents of green C. subternata was investigated. By steaming green C. subternata directly after maceration, its colour retention can be improved. Good stability was shown for mangiferin and hesperidin during manufacture and storage of C. subternata.

Thesis (MSc Food Sc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Kefir is a fermented dairy beverage resulting from the fermentation of milk with reusable Kefir grains. The grains consist of a complex combination of lactic acid bacteria and yeasts in a symbiotic relationship, embedded in a polysaccharide matrix called kefiran. Various problems are experienced during the commercialisation of the ready-made Kefir beverage and, therefore, it is more advantageous to market the grains, enabling the consumer to produce the beverage at home. Kefir grains could be mass-cultured and then preserved by Iyohilisation for successful long-term storage and easy distribution, during commercialisation. The microbial balance of the Kefir grains changes during both mass-culturing and freeze-drying, which will have an influence on the sensory properties of the Kefir beverage produced. The aim of this study was the optimisation of the production of Kefir from mass-cultured grains and from freezedried mass-cultured grains respectively. The sensory characteristics of the fermented beverages produced from these mass-cultured and preserved grains were determined. Mass-cultured Kefir grains were activated and Kefir produced using nine methods with different activation times and temperatures, different grain:milk ratios (36, 72 and 108 g grains.l⁻¹) and with different heat-treated milks (pasteurised, double pasteerised and UHT). The best Kefir beverage was produced by activation of the grains at 22°C for two successive 24 h incubation periods, followed by Kefir production at 22°C for 18 h and a maturation period at 18°C for 6 h. The milk was replaced before every incubation period, excluding the maturation period, and the fermentation vessel was swirled five times at the start of fermentation and after 18 h. This method resulted in a sour beverage with a thick consistency and the characteristic effervescence and flavour of Kefir. The optimal grain:milk ratio was identified as 36 g grains.l⁻¹ and the best heat-treated milks for the production of Kefir beverage were UHT and double pasteurised milk. Mass-cultured Kefir grains were freeze-dried for 1, 2, 3 and 6 d and the moisture loss determined. Freeze-dried grains were rehydrated for 1, 2, 6, 12 and 18 h to determine the optimal rehydration time. A sensory analysis was performed to compare the properties of Kefir produced from mass-cultured grains (Me), freeze-dried mass-cultured grains that were rehydrated and activated (FDRA) and activated mass-cultured grains that were freeze-dried and rehydrated (AFDR). The chemical compositions of mass-cultured grains (MC), mass-cultured, freezedried grains (MCFD), mass-cultured, freeze-dried grains that were rehydrated and activated (FDRA) and activated mass-cultured grains that were freeze-dried and rehydrated (AFDR), were also investigated. The optimum time to freeze-dry grains was 2 d and to rehydrate freeze-dried gtains was 1 h. The sensory analysis indicated that Kefir beverages prepared from FDRA and AFDR grains did not differ significantly and were less fermented than Kefir produced from MC grains. It was concluded that Kefir with excellent sensory characteristics can be produced from mass-cultured grains. Freeze-drying is a better method to preserve Kefir grains than freezing due to mass loss during freezing and easier distribution and storage of freeze-dried grains. The supplementation of freeze-dried grains with additional lactic acid bacteria and yeast isolates should be investigated. / AFRIKAANSE OPSOMMING: Kefir is 'n gefermenteerde suiwelproduk wat geproduseer word deur die fermentasie van melk met herbruikbare Kefirkorrels. Die korrels bestaan uit 'n komplekse kombinasie van melksuurbakterië en giste en is ingebed in 'n polisakkaried matriks genaamd kefiran. Verskeie probleme word ondervind met die kommersialisering van die klaar voorbereide Kefirdrankie en dit is meer voordelig om die korrels te bemark. Dit sal die verbruiker daartoe in staat stel om self Kefir tuis te produseer. Kefirkorrels kan in massa gekweek word en dan gevriesdroog word om langtermyn storing en verspreiding te vergemaklik tydens kommersialisering. Die spesifieke mikrobiese balans van die Kefirkorrels word tydens massakweking en vriesdroging versteur. Dus sal hierdie twee prosesse 'n invloed hê op die sensoriese eienskappe van die Kefir drankie geproduseer. Die doel van hierdie studie was die optimisering van die produksie van Kefir vanaf massagekweekte korrels en gevriesdroogde massagekweekte korrels. Die sensoriese karakteristieke van die Kefir geproduseer met hierdie korrels is ondersoek. Massagekweekte Kefirkorrels is geaktifeer en Kefir is geproduseer met nege verskillende metodes met variasies in die tyd en temperatuur kombinasies, verskillende korrel:melk verhoudings (36, 72 en 108g korrels.l⁻¹) en verskillende hittebehandelde melke (gepasteuriseerd, dubbel gepasteuriseer en UHT). Die beste Kefirdrankie is geproduseer deur die aktivering van die korrels by 22°C vir twee 24 h inkubasieperiodes, gevolg deur Kefir produksie by 22°C vir 18 uur en 'n verouderingsperiode by 18°C vir 6 h. Die melk was voor elke inkubasieperiode vervang, uitsluitende die verouderingsperiode. Die fermentasie houer is vyf maal gedraai aan die begin van fermentasie en na 12 h. Hierdie metode het gelei tot 'n drankie wat suur was met 'n dik konsistensie en die karakteristieke vonkeling en geur van Kefir. Die optimale korrel:melk ratio is geidentifiseer as 36 9 korrels.l⁻¹ en die verkieslike hittebehandelde melke is dubbel gepasteuriseerde en UHT melk. Massagekweekte Kefirkorrels was vir 1, 2, 3 en 6 dae gévriesdroog en die massaverlies is bepaal. Gevriesdroog korrels is gerehidreer vir 1, 2, 6, 12 en 18 h om die optimale rehidrasietyd te bepaal. 'n Sensoriese analise is uitgevoer om die eienskappe te vergelyk van Kefir geproduseer van massagekweekte korrels (MC), gevriesdroogde massagekweekte korrels wat gerehidreer en geaktiveer is (FDRA) en geaktiveerde massagekweekte korrels wat gevriesdroog en gerehidreed is (AFDR). Die chemiese samestelling van massagekweekte korrels (MC), massagekweekte, gevriesdroogde korrels (MCFD), massagekweekte, gevriesdroogde korrels wat gerehidreer en geaktiveer is (FDRA) en geaktiveerde massagekweekte korrels wat gevriesdroog en gerehidreer is (AFDR), is bepaal. Die optimum tydperk vir vriesdroging van korrels was 2 d en vir rehidrasie van gevriesdroogde korrels was 1 h. Die sensoriese analise het aangedui dat Kefir wat van FDRA en AFDR korrels geproduseer is, nie betekenisvol van mekaar verskil het nie, maar minder gefennenteerd was as Kefir wat van Me korrels geproduseer is. Die gevolgtrekking is gemaak dat 'n Kefirdrankie met uitstekende eienskappe geproduseer kan word met massagekweekte korrels. Vriesdroging is 'n beter metode as bevriesing om Kefirkorrels te preserveer a.g.v die ver1iesvan massa tydens bevriesing en die vergemakliking van vervoer en verspreiding van gevriesdroogde korrels. Die aanvulling van gevriesdroogde korrels met addisionele melksuurbakterieêen giste moet nog ondersoek word.

Thesis (MSc Food Sc.)--Stellenbosch University, 1964. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MSc Food Sc )--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Drying of fruit is an age-old preservation technique that even to this day, remains popular. On the foreign markets there is a trend towards dried fruit products that are softer and more palatable. Based on this, the South African dried fruit industry has launched a range of "soft eating", high moisture dried fruit (HMOF) products. These products have a moisture content of ca 36% (w/w) and a water activity (aw) of ca 0.85, both of which are considerably higher than that of traditional dried fruit. It is this higher moisture content that makes the product susceptible to serious microbial spoilage and colour deterioration in spite of the use of sulphur dioxide. Currently, the shelf-life of these products is approximately three months and to ensure a quality export product, the shelf-life must be at least nine months. During this study the microbial composition of five South African commercially available HMDF products (raisins, prunes, nectarines, cling stone peaches and apricots), was determined. It was found that high moisture dried (HMO) raisins and prunes had the highest bacterial counts, while apricots were more susceptible to yeast and mould spoilage. The most frequently isolated microbes were members of the endospore forming Bacillus group and osmotolerant yeasts like Zygosaccharomyces. Members of the genera Salmonella, Staphylococcus and even anaerobic endospore formers were present in certain samples of the HMO prunes and raisins. From these results it was concluded that the current pasteurisation method of 7 h at 80°C used by the industry is not effective in successfully eliminating spoilage microbes. High moisture dried nectarines and prunes were used in challenging studies, where four indicator organisms (B. cereus, Z. rouxii, Escherichia coli and Penicillium chrysogenum) were selected to evaluate the shelf-stability of these two HMOF products over six months at 5° and 25°C. The results showed higher bacterial counts for the fruit stored at 25°C (1 200 cfu.g ̄ ¹ versus 450 cfu.g ̄ ¹ at 5°C), as well as extensive Maillard browning of the nectarines at the higher storage temperature. Furthermore, it was found that the pasteurisation method (7 h at 80°C) was not effective in eliminating the endospore former B. cereus, P. chrysogenum and Z. rouxii, which may thus lead to serious spoilage implications. The E. coli strain did not survive in either of the HMOF products and no counts were found even before pasteurisation. From these results it was clear that the current pasteurisation method of HMOF products is not effective in terms of the prevention of spoilage, and that storage of the product at lower temperatures would lead to a better quality product. The impact of different preservatives (lysozyme, pimaricin, sorbate, benzoate and an imidazole compound) on the survival and growth of B. cereus and Z. rouxii, were evaluated in nectarine puree prepared from dried nectarines. Lysozyme showed the best inhibitory effect (70% inhibition) on B. cereus over a 12 h incubation period, followed by benzoate, sorbate, the imidazole compound and lastly, pimaricin. The data obtained for the inhibitory effect of the preservatives on Z. rouxii showed that benzoate and sorbate showed. the best growth inhibitory effect (100% inhibition after 24 h). Pimaricin gave a 100% inhibitory effect after 48 h while the imidazole compound gave a 89% inhibition. From the different pasteurisation time/temperature combinations applied to eliminate the endopspore former B. 'cereus, it was found that pasteurisation of 150 min at 90°C showed the best inhibition results. However, the colour of the product was unstable. It was, therefore, decided to also evaluate the use of modified atmosphere packaging (MAP), as part of the product's processing. It was found that the colour of the HMO nectarines was stable and it is thus recommended that a time/temperature combination of 150 min at 90°C together with MAP, is used to ensure a shelf-stable HMOF product. / AFRIKAANSE OPSOMMING: Die droging van vrugte is 'n eeu-oue preserveringstegniek wat vandag steeds baie gewild is. Daar is 'n tendens in die oorsese markte na droëvrugte wat sagter en smaakliker is. Gebaseer op hierdie tendens het die Suid Afrikaanse droëvrugtebedryf 'n nuwe "soft eating", hoë vog droëvrug (HVDV) produkreeks die lig laat sien. Hierdie produkte het 'n voginhoud van ca 36% (m/m) en 'n water aktiwiteit (aw) van ca 0.85. Dit is die hoër voginhoud wat lei tot mikrobiologiese bederf en verbruining. Tans is die rakleeftyd van die produkte ongeveer drie maande, terwyl uitvoer standaarde 'n rakleeftyd van minstens nege maande vereis. Tydens hierdie studie is die mikrobiese samestelling van vyf Suid Afrikaans beskikbare HVDV produkte (rosyne, pruimedante, nektariens, taaipit perskes en appelkose) bepaal. Dit is bevind dat hoë vog droë (HVD) rosyne en pruimedante meestal hoë bakterie tellings het, terwyl appelkose meer vatbaar is vir giste en misiliêre fungi. Die organismes wat meestal geïsoleer is, was lede van die endospoorvormende Bacillus groep en osmotolerante giste soos Zygosaccharomyces. Lede van die genera Salmonella, Staphylococcus en selfs anaerobiese endospoorvormers is gevind in van die HVD pruimedante en rosyne. Vanuit hierdie resultate was dit duidelik dat die huidige pasteurisasie proses van 7 h by 80°C, wat deur die industrie gebruik word, nie effektief is om bederf organismes suksesvol te elimineer nie. Hoë vog droë nektariens an pruimedante is gebruik in uitdaging studies, waar vier indikator organismes (B. cereus, Z. rouxii, Escherichia coli en Penicillium chrysogenum) gekies is, om die rakleeftyd van die twee HVDV produkte oor 'n opbergingstydperk van 6 maande by 5° en 25°C te evalueer. Die resultate het hoër bakteriese tellings vir vrugte wat by 25°C (1 200 kve.g ̄ ¹ versus 450 kve.g ̄ ¹ by 5°C) opgeberg is getoon, asook dat Maillard verbruining by HVD nektariens plaasvind by die hoër opbergingstemperatuur. Verder is bevind dat die pasteurisasie metode (7 h by 80°C) nie effektief was om die endospoorevormer B. cereus, P. chrysogenum en Z. rouxii te elimineer nie, wat ernstige bederf implikasies tot gevolg kan hê. Die E. coli stam het nie in een van die twee HVDV produkte oorleef nie en geen tellings is gevind nie, selfs nie voor pasteurisasie nie. Die resultate het duidelik getoon dat die huidige pasteurisasie proses vir HVDV nie effektief is om mikrobiese bederf te voorkom nie, terwyl 'n lae opbergingstemperatuur aanbeveel word om 'n beter kwaliteit eindproduk te verseker. Die impak van verskillende preserveermiddels (lisosiem, pimarisien, sorbaat, bensoaat en 'n imidasool verbinding) ten opsigte van die groei en oorlewing van B. cereus en Z. rouxii is geëvalueer in nektarien puree. Lisosiem het die beste inhibisie effek (70% inhibisie) t.o.v. B. cereus getoon gedurende die 12 h inkubasie periode, gevolg deur bensoaat, sorbaat, die imidasool verbinding en laastens pimarisien. Die data verkry vir die inhibitoriese effek van die preserveermiddels t.o.v Z. rouxii, het getoon dat bensoaat en sorbaat die beste groei inhibisie getoon het (100% inhibisie na 24 h). Pimarisien het 'n 100% inhibisie getoon na 48 h, terwyl die imidasool verbinding 89% inhibisie getoon het. Van die verskillende pasteurisasie kombinasies wat aangewend is om die endopsoorvormer B. cereus te elimineer, is dit bevind dat 'n pasteurisasie van 150 min by 900G die beste inhibisie resultate getoon het. Die kleur van die nektariens was egter onstabiel. Gevolglik is daar besluit om gemodifiseerde atmosfeer verpakking (MAV) te evalueer as deel van die produk se prosessering. Dit is bevind dat die kleur van die HVD nektariens stabiel was en daar word verder aanbeveel om 'n tyd/temperatuur kombinasie van 150 min by 90°C, saam met MAV te gebruik, om 'n kwaliteit eindproduk te verseker.

Thesis (PhD(Food Sc))--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In Southern Africa, the hunting of wildfowl species has increased considerably in the past few years. Crop farmers incur major financial losses due to the feeding activities of Egyptian geese (Alopochen aegyptiacus); consequently a large number of geese are hunted in an attempt to reduce the damage caused. With the current absence of scientific information baseline research investigating the meat quality of this species is essential. The sensory profile of Egyptian goose meat was found to be very distinct in relation to the characteristics of other well-known fowl species. It has very strong game aroma and flavour attributes with a prominent metallic aftertaste. The intense aroma and flavour notes were linked to the substantially higher iron content, as well as the high overall polyunsaturated fatty acid content as revealed by chemical profiling. The trained sensory panel also found the meat to be very tough (high shear force) compared to the other species. To identify the factors which may affect the overall consistency of the meat quality, the influence of three main effects namely; season (grain vs. non-grain diet), gender and portion was investigated. This revealed that season had the largest effect and harvesting periods should therefore be considered. The main issue is the higher intramuscular fat (IMF) content in winter (July), as well as the substantial difference in the fatty acid profiles of the two seasons. The forage vs. grain based diets during certain periods of the year leads to variation in the content of key fatty acids in the meat i.e. oleic acid, linoleic acid and α-linolenic acid. In winter, the meat had a characteristic, prominent game and metallic aroma while the summer (November) profile was governed by “sweet-oily-duck” and beef-like sensory notes. The fatty acid differences also result in variation between the omega 6 to omega 3 ratios of the seasons; the portions from winter are within the recommendations (ratio<5) and those from summer not. Regarding gender, the females had a lower carcass yield but higher IMF content. The female breast portion was also more tender (lower shear force). In attempting to elucidate the toughness of the meat, possible causes have been proposed. The pH decline in the pectoralis muscle occurs quite rapidly and it is possible that the high rigor temperature (>20 °C) may contribute to the increased toughness. Regardless of the proteolytic enzyme activity during the rigor period, the meat is still tough at 36 h post mortem and the proteolytic contribution may be overshadowed by the background toughness, i.e. the connective tissue content and fibre structure. The latter was confirmed when the breast portions were aged for 14 days and no change (decline) in the shear force values was observed even though myofibrillar degradation did occur (during ageing). Given the lack of a decline in the shear force, the aging of Egyptian goose meat as a means of improving the overall toughness cannot be proposed without further research. The study in its entirety provides substantial proof that the commercial utilisation of Egyptian goose meat is feasible. / AFRIKAANSE OPSOMMING: Die jag van wildsvoël spesies in Suider-Afrika het aansienlik toegeneem in die laaste paar jaar. Graanboere lei jaarliks groot finansiële verliese as gevolg van die voedingsgedrag van kolganse (Alopochen aegyptiacus). Gevolglik word ‘n groot hoeveelheid ganse elke jaar geoes om sodoende die skade te verminder. Met die huidige tekort aan wetenskaplike inligting is grondslag navorsing rakende die vleiskwaliteit van hierdie wildsvoël spesie noodsaaklik. Die sensoriese profiel van kolgansvleis is baie uniek in vergelyking met die vleis van ander bekende voël spesies. Dit word gekenmerk deur die sterk wildagtige aroma en geur tesame met ‘n baie prominente metaal nasmaak. Hierdie intense aroma en geur hou verband met ‘n baie hoër yster-inhoud, asook ‘n hoë poli-onversadigde vetsuur profiel soos uitgewys deur die chemiese karakteriserings studie. Die opgeleide sensoriese proepaneel het ook die vleis van hierdie voël spesie beskou as baie taai in vergelyking met die vleis van ander spesies. Ten einde te bepaal watter faktore die algehele variasie in vleiskwaliteit sal beïnvloed, is drie hoofeffekte naamlik, seisoen (graan teenoor nie-graan dieet), geslag en porsie ondersoek. Die verskeie studies het uitgewys dat seisoen die grootste invloed het en daarom sal die periodes waarin ganse geoes word in ag geneem moet word. Die hoër intramuskulêre vetinhoud in winter (Julie), asook die aansienlike verskil in die vetsuur profiele van die twee seisoene is die vernaamste verskille. Die weiding (hoofsaaklik gras) teenoor graan diëte wat gevolg word in sekere dele van die jaar lei tot variasie in die inhoud van belangrike vetsure (oliensuur, linoleïensuur en α-linoleensuur) in die vleis. In die winter het die vleis die kenmerkende en prominente wild geur en metaalagtige nasmaak getoon terwyl die profiel in die somer (November) hoofsaaklik bestaan het uit “soet-olierige-eend” en beesvleis geure. Die vetsuur verskille lei ook tot ‘n verskil in die omega-6 tot omega-3 verhouding van die seisoene; in die winter is die porsies binne die aanbevole voedingsvereistes (<5) terwyl die somer porsies nie aan hierdie vereistes voldoen het nie. Rakende die invloed van geslag, het die vroulike voëls ‘n laer karkas massa getoon tesame met ‘n laer intramuskulêre vetinhoud. Die borsie van die vroulike kolganse was ook sagter. In ‘n poging om die taaiheid van kolgansvleis te verklaar, is ‘n paar moontlike oorsake voorgestel. Die na-doodse pH daling in die borsspier vind redelik snel plaas, daarbenewens is dit ook moontlik dat die hoë temperature (>20 °C) waartydens rigor mortis plaasvind, kan bydrae tot die taaiheid. Ongeag die werking van die proteolitiese ensieme tydens die rigor periode was die vleis steeds taai 36 uur na dood, daarom was die proteolitiese bydrae moontlik oorskadu deur die agtergrond-taaiheid, dit wil sê die bindweefsel inhoud en vesel struktuur. Laasgenoemde is bevestig toe die borsspiere verouder is vir ‘n tydperk van 14 dae. Geen verandering (afname) in die instrumentele taaiheid is waargeneem nie, selfs al het miofibrillêre afbraak plaasgevind. Aangesien daar geen afname in instrumentele taaiheid opgemerk is nie kan veroudering van kolgansvleis, met die doel om die taaiheid te verbeter, nie aanbeveel word voor verdere navorsing nie. In geheel voorsien hierdie studie beduidende motivering rakende die moontlike kommersiële aanwending van kolgansvleis.

Thesis (PhD (Food Science))--University of Stellenbosch, 2006. / High-rate anaerobic bioreactors are used for the treatment of various wastewaters, of which the upflow anaerobic sludge blanket (UASB) bioreactor has the widest application, especially in the food and beverage industries. In an UASB bioreactor sludge develops in a particular granular or flocculent form and the success of the anaerobic process relies on the formation of active and settable granules. These granules are formed by self-aggregation of bacteria that can be divided into different trophic groups that are responsible for the metabolic breakdown of organic substrates. The successful performance of a bioreactor is influenced by the composition of the substrate which subsequently may have an impact on the microbial consortium present in the UASB granules. In order to determine if a change in the structure of the non-methanogenic microbial community takes place, UASB brewery granules were subjected to the sudden addition of different carbon sources at different concentrations. A shift in the microbial community did occur when the granules were subjected to lactate medium (5 g.l-1). No changes in the microbial community were observed when the granules were stressed with glucose medium as carbon source, regardless of an increase in the glucose concentration. In order to better understand the effect that different wastewaters may have on the microbial consortium present in different UASB granules, the polymerase chain reaction (PCR) based denaturing gradient gel electrophoresis (DGGE) technique and sequence analysis were used to fingerprint and identify the Bacteria and Archaea present in either, winery, brewery, distillery or peach-lye canning UASB granules. Each granule type showed distinct PCR-based DGGE fingerprints with unique bands, while other bands were found to be present in all the granules regardless of the wastewater being treated. Bacillus, Pseudomonas, Bacteroides, Enterococcus, Alcaligenes, Clostridium, Shewanella, Microbacterium, Leuconostoc, Sulfurospirillum, Acidaminococcus, Vibrio, Aeromonas, Nitrospira, Synergistes, Rhodococcus, Rhodocyclus, Syntrophobacter and uncultured bacteria were identified, representing different acidogenic, acetogenic and homoacetogenic Bacteria.Different methanogenic bacteria such as Methanosaeta, Methanosarcina, Methanobacterium and uncultured bacteria belonging to the group Archaea were also fingerprinted and identified from different UASB granules. In both these studies a DGGE marker was constructed that may be used to assist in the identification of bacteria. The DGGE marker can also be used to monitor the presence of bacteria over a time period during anaerobic digestion. Bioaugmentation or the enrichment of granules results in tailor-made granules that may be used for the treatment of specific wastewaters. One of the most important contributions to the maintenance and enhancement of UASB granule formation is the inclusion of suitable microbes in the granule structure. Enterobacter sakazakii was isolated from raw winery wastewater and was found to produce sufficient amounts of desired fatty acids. This bacteria was, therefore, incorporated into batch cultured granular sludge. In order to identify and monitor the presence of the incorporated E. sakazakii in the tailor-made granules, 16S rRNA gene sequence primers and PCR conditions were developed. The use of molecular techniques such as PCR-based DGGE and sequence analysis proved to be successful methods to fingerprint and identify the microbial consortium present in the different UASB granules.

Thesis (PhD (Food Sc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Consumers have the right to accurate information on the fish products they purchase to enable them to make educated seafood selections that will not endanger their own wellbeing or the wellbeing of the environment. Unfortunately, marine resource scarcity, financial incentives and inadequate or poorly enforced regulations have all promoted the mislabelling of fish species on global markets, the results of which may hold economic, conservation and health consequences. The primary aims of this study were to determine the most commonly available fish species on the South African market, to establish and compare DNA-based methods for the unambiguous identification of these species and to utilise the most applicable methods to evaluate the extent of mislabelling on the local fisheries market. The results from surveys of n = 215 restaurants and n = 200 retail outlets in four South African provinces (Western Cape, Kwa-Zulu Natal, Eastern Cape and Gauteng) indicated that 34 and 70 nominal fish types were available in restaurants and retail outlets, respectively, the most common of which were kingklip, salmon and hake. Over 30% of the fish species being sold were of conservation concern, while several outlets marketed specially-protected, illegal-to-sell species in South Africa. Fish purveyors were poorly equipped to provide information on the identity, origin, production method (farmed/wild) and sustainability of the fish they were selling and the labelling of many packaged fish products was in contravention with South African regulations. Data were published for the first time comparing the efficiency of five methods (urea-SDS-proteinase K, phenol-chloroform, salt extraction, SureFood PREP kit and Wizard Genomic DNA Purification kit) for the extraction of DNA from the muscle tissue of fish species available in South Africa. The SureFood kit was identified as the most suitable method for DNA extraction from fish muscle, extracting significantly (P < 0.05) higher DNA yields than all other methods evaluated and being simple and safe to use. A comprehensive reference library of genetic information was compiled for the first time that contains sufficient DNA sequence data from different mitochondrial DNA loci (16S ribosomal RNA (rRNA), 12S rRNA and cytochrome c oxidase I (COI) genes, as well as the control region) to allow the explicit identification of 53 fish species in South Africa. Although 16S and 12S rRNA gene sequencing allowed the identification of most fish to the genus level, the discrimination of closely-related, congeneric species was problematic when based on these gene regions. Conversely, the vast majority (98%) of fish examined could be readily differentiated by their COI sequences, with only members of the genus Thunnus requiring supplementary control region sequencing for species confirmation. Lastly, sequencing of the COI region was used to show that 9% of fish samples collected from local seafood wholesalers and 31% of samples from retail outlets were mislabelled. This study has established that fish mislabelling is a reality on the South African market and that DNA-based methods should be applied by both industry and regulatory bodies to deter illegal activities and to promote transparency on the domestic fisheries market. / AFRIKAANSE OPSOMMING: Verbruikers het die reg tot akkurate informasie rakende die visprodukte wat hulle aankoop. Hierdie inligting sal hulle bemagtig om ingeligte seekos keuses te maak wat voordelig sal wees vir beide die verbruiker se eie, sowel as die omgewing, se voortbestaan. Ongelukkig het 'n gebrek aan seelewebronne, geldelike aansporings en onvanpaste of swak geïmplimenteerde regulasies gelei tot die verkeerde etikettering van visspesies op die wêreldmarkte. Dit mag ekonomiese-, bewarings- en gesondheidsgevolge inhou. Die primêre doelwitte van hierdie studie was om te bepaal watter visspesies die algemeenste beskikbaar is in die Suid-Afrikaanse mark, om DNS-gebaseerde metodes vir die duidelike identifisering van hierdie spesies te vind en te vergelyk, en om die mees gepaste metodes te gebruik om die omvang van verkeerde etikettering in die plaaslike vismarkte te evalueer. Die resultate van opnames van n = 215 restaurante en n = 200 winkels in vier Suid-Afrikaanse provinsies (Wes-Kaap, Kwa-Zulu Natal, Oos-Kaap en Gauteng) het gewys dat 34 en 70 nominale visspesies in onderskeidelik restaurante en kleinhandelaars beskikbaar was. Koningklip, salm en stokvis was die mees algemene spesies. Meer as 30% van die visspesies wat te koop was is van bewaringsbelang, terwyl verskeie winkels spesiaal-beskermde, onwettig-om-te-verkoop spesies in Suid-Afrika bemark het. Visverkopers was swak bemagtig om informasie oor die identiteit, oorsprong, produksiemetode (teel/wild) en volhoubaarheid van die vis wat hulle verkoop het te kon gee. Verder was die etikettering van baie verpakte visprodukte in stryd met Suid-Afrikaanse regulasies. Vir die eerste keer is data gepubliseer wat vyf metodes (ureum-SDS-proteïenase K, fenolchloroform, sout-ekstraksie, SureFood PREP stel en Wizard Genomic DNS suiwering stel) vergelyk in hul doeltreffendheid om DNS vanuit die spierweefsel van visspesies wat in Suid-Afrika beskikbaar is te ekstraheer. Die SureFood stel is as die mees geskikte metode vir DNS ekstraksie vanuit visweefsel geïdentifiseer aangesien die DNS opbrengs betekenisvol (P < 0.05) hoër was met hierdie metode, en dit ook 'n eenvoudige en veilige metode is om te gebruik. 'n Omvattende verwysingsbiblioteek van genetiese informasie wat voldoende DNS volgordebepalingsdata van verskillende mitokondriale DNS lokusse (16S ribosomale RNS (rRNS), 12S rRNS en sitochroom c oksidase I (COI) gene, sowel as die kontrolegebiede) bevat, is vir die eerste keer opgestel om die besliste identifisering van 53 visspesies in Suid-Afrika toe te laat. Alhoewel 16S en 12S rRNS geenvolgordebepaling die identifisering van meeste visse op genusvlak toegelaat het, was die diskriminasie van naby-verwante, gelyksoorting spesies problematies wanneer hierdie geengebiede gebruik is. Die oorgrote meerderheid (98%) vis wat ondersoek is geredelik onderskei op grond van hul COI volgordebepalings, met slegs lede van die genus Thunnus wat addisionele kontrolegebied volgordebepaling vir spesies bevestiging vereis het. Laastens, is volgordebepaling van die COI-gebied gebruik om te wys dat 9% van die vismonsters van plaaslike seekosgroothandelaars en 31% van die monsters van kleinhandelaars verkeerd geëtiketteer is. Hierdie studie het bevestig dat die verkeerde etikettering van vis in Suid-Afrika 'n realiteit is, en dat DNS-gebaseerde metodes gebruik moet word deur die industrie sowel as die regulerende liggame om onwettige aktiwiteite teen te werk en om deursigtigheid in plaaslike vismarkte te bevorder.

Thesis (PhD Food Sc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The fermentation of milk has been known for millennia and leads to nutritious and prolonged shelf-life dairy products. In Southern Africa, traditional fermented dairy products have the same value as local staple foods and are consumed as a part of or as a whole meal. However, the retail price and the technology make many commercialised fermented dairy products unaffordable to the majority of the population. There is thus a need for a healthy nutritious low-cost easily prepared fermented dairy product. A product that could be the answer to the above need, is Kefir. The principle advantage is that the Kefir beverage is made from reusable Kefir grains, which unfortunately are not easily available and grow slowly. Kefir grains can only be obtained from pre-existing grains, which presents a problem in the marketing of the grains. A mass culturing technique was developed to produce large masses of grains but preparation of Kefir using these grains results in a product (MG Kefir) lacking in the sensory attributes of Traditional Kefir. Thus, the overall objective of this research was to determine the impact of environmental factors on the metabolic profiles of Kefir produced using different Kefir grains and this was then followed by the subsequent enrichment of Kefir prepared with mass cultured grains so as to obtain a Kefir beverage that has improved organoleptic qualities. To determine the impact of environmental factors Traditional and MG Kefir were prepared under controlled and uncontrolled conditions. Traditional Kefir was found to give the best beverage and was thus considered as the control. Under controlled conditions the optimum incubation temperature for the production of Kefir was 22ºC as over-acidification was observed at 25ºC. The metabolic profiles of both Traditional and MG Kefir showed that both contained acetaldehyde, ethanol, acetone, diacetyl and acetic acid. In addition, the metabolic profiles revealed that an inadequate ratio of diacetyl to acetaldehyde as well as the lack of ethyl acetate was responsible for the flavour defect in MG Kefir. In order to overcome this defect, citrate and ascorbate (0.015 % w.v-1) were added during Kefir fermentation to enhance the diacetyl and ethyl acetate production. This addition showed a positive impact on diacetyl but not on ethyl acetate production. Improvement of the overall flavour of Kefir was observed as the ratios of diacetyl to acetaldehyde were higher (0.21 – 0.5) in the samples with added citrate and ascorbate than in the samples without (0.12 – 0.17). The production of ethyl acetate in MG Kefir was enhanced by combining the effects of longer incubation (24 h + 18 h at 22ºC), addition of ethanol and acetic acid at 0.79% (m.v-1) and the addition of either Lactococcus lactis ssp. diacetylactis biovar diacetylactis 318 or Candida kefyr 1283. The best yields were obtained in samples containing C. kefyr 1283 and only added ethanol (9.22 mg.L-1), indicating that ethanol is an important factor in ethyl acetate production by Kefir starter strains and suggesting that the absence of ethyl acetate is an indication that the grains do not contain a yeast capable of producing sufficient ethyl acetate. During this investigation, the impact of ethyl acetate on the organoleptic quality of Kefir during storage at refrigerated and room temperatures were also studied. The results indicated that refrigerated Kefir contained up to 40 mg.L-1 of ethyl acetate and was not found defective and thus ethyl acetate was considered a positive contributor to Kefir flavour. This is of particular interest as ethyl acetate is a potent flavour compound at concentrations below 5 mg.L-1. Improvements of MG Kefir’s flavour were successful and will be of value for commercial Kefir production where the main aim is to optimise the flavour of Kefir. However, stabilising the grain microbial consortium was found to be important as it is responsible, over time, for both stable and acceptable Kefir. Acceptability of Traditional, MG and other Kefirs (Candi-Kefir and Lacto-Kefir) prepared with microbially stabilised MG was evaluated by 85 consumers. Results indicated that pH (r = 0.978; p < 0.05) was a significant driver of liking for flavour, especially for female consumers (r = 0.982; p < 0.05). In addition, three clusters, each characterised by different liking attributes were identified. Cluster I generally disliked all the products whereas slight acidic Kefir such as Candi-Kefir (7.63) and Lacto-Kefir (7.09) were preferred by Cluster III. Cluster II showed preference to Kefir with moderate acidity and high ethanol content. In that regard, Traditional Kefir obtained the best score (7.50) and MG Kefir the lowest score (4.87). The sensory study is of value as it led to the identification of the drivers of consumers liking by the different types of consumers. In the course of this project, near infrared reflectance spectroscopy was developed as a rapid method to estimate lactic and acetic acids, which are the organic acids responsible for acidity in Kefir, as well as pH and titratable acidity (TA). The results showed that the calibration models for lactic acid (RPD = 2.57 – 3.16), pH (RPD = 2.90) and TA (RPD = 2.60) were good for screening purposes (2 < RPD < 3); indicating that these models would show if the concentrations of lactic acid, the pH or the TA varied from the normal range. This study has demonstrated that the flavour of MG Kefir, prepared with enriched grains, was successfully improved and has provided some understanding on the preference liking of Kefir, an unknown fermented dairy product to South African consumers. / AFRIKAANSE OPSOMMING: Die fermentering van melk is al vir millennia bekend en lei tot voedsame suiwelprodukte met 'n verlengde raklewe. In Suidelike Afrika het tradisioneel gefermenteerde suiwelprodukte dieselfde waarde as plaaslike stapelvoedsels en word dit as 'n maaltyd of as deel van 'n maaltyd geëet. Die kleinhandelsprys en tegnologie van kommersieel gefermenteerde suiwelprodukte maak hierdie produkte egter onbekostigbaar vir die grootste deel van die populasie. Daar is dus 'n behoefte aan 'n gesonde, voedsame, goedkoop, maklik-om-te-berei gefermenteerde suiwelproduk. 'n Moontlike produk om aan die bogenoemde te voldoen is Kefir. Die hoof voordeel is dat die Kefir drankie van herbruikbare Kefirkorrels gemaak word, maar ongelukkig is hierdie korrels nie vrylik beskikbaar nie, en vermeerder dit stadig. Kefirkorrels kan net van reeds bestaande korrels verkry word wat problematies is vir die bemarking van hierdie korrels. 'n Massakwekingstegniek is ontwikkel vir die produksie van groot hoeveelhede korrels maar die voorbereiding van Kefir met hierdie korrels lei tot 'n produk (MG Kefir) wat sensories minder aanvaarbaar is as tradisionele Kefir. Die hoofdoel van hierdie navorsing was dus om die invloed van omgewingsfaktore op die metaboliese profiele van Kefir, berei deur gebruik te maak van verskillende Kefirkorrels, te bepaal. Dit is gevolg deur die verryking van Kefir berei van massagekweekte korrels om 'n Kefir drankie met verbeterde organoleptiese kwaliteite te verkry. Tradisionele en MG Kefir is voorberei onder gekontroleerde en ongekontroleerde toestande om die impak van omgewingsfaktore te bepaal. Die beste drankie is van tradisionele Kefir verkry en is dus beskou as die kontrole. Die optimum temperatuur vir die produksie van Kefir onder gekonroleerde toestande is 22ºC aangesien oor-versuring by 25ºC waargeneem is. Die metaboliese profiele van beide tradisionele en MG Kefir het gewys dat beide produkte asetaldehied, etanol, asetoon, diasetiel en asynsuur bevat. Die metaboliese profiele het verder gewys dat 'n onvoldoende diasetiel tot asetaldehied verhouding sowel as 'n tekort aan etielasetaat verantwoordelik was vir 'n geur defek in MG Kefir. Om hierdie defek te oorkom is sitraat en askorbaat (0.015% m.v-1) tydens Kefir fermentasie bygevoeg om diasetiel en etielasetaat produksie te verhoog. Hierdie byvoeging het 'n positiewe effek gehad op diasetiel produksie, maar nie op die produksie etielasetaat nie. 'n Verbetering in die algehele geur van Kefir is waargeneem aangesien die diasetiel tot asetaldehied verhoudings hoër (0.21 – 0.5) was in die monsters met bygevoegde sitraat en askorbaat as in die monsters daarsonder (0.12 – 0.17). Die produksie van etielasetaat in MG Kefir is verhoog deur die effekte van 'n verlengde inkubasie tydperk (24 h + 18 h by 22ºC), die byvoeging van etanol en asynsuur teen 0.79% (m.v-1) en die byvoeging van óf Lactococcus lactis ssp. diacetylactis biovar diacetylactis 318 óf Candida kefyr 1283 te kombineer. Die beste opbrengs is verkry in monsters wat C. kefyr 1283 en slegs etanol (9.22 mg.L-1) bevat het. Dit dui daarop dat etanol 'n belangrike faktor is vir etielasetaat produksie in Kefir beginstamme en wys moontlik op die afwesigheid van etielasetaat wat daarop dui dat die korrels nie 'n gis bevat wat bevoeg is om genoegsame hoeveelhede etielasetaat te produseer nie. Tydens hierdie ondersoek is die impak van etielasetaat op die organoleptiese kwaliteit van Kefir gedurende opberging by verkoelde- en kamertemperatuur ook bestudeer. Die resultate het gewys dat verkoelde Kefir tot 40 mg.L-1 etielasetaat bevat het sonder dat dit defektief was. Etielasetaat is dus beskou as 'n positiewe bydraer in terme van Kefir geur. Dit is van besondere belang aangesien etielasetaat 'n sterk geurkomponent teen konsentrasies laer as 5 mg.L-1 is. Verbeteringe in MG Kefir se geur was suksesvol en sal van waarde wees vir kommersiële Kefir produksie waar die hoofdoel die optimisering van Kefir geur is. Stabilisering van die korrels se mikrobiologiese konsortium is ook belangrik aangesien daar gevind is dat dit oor tyd verantwoordelik is vir stabiele en aanvaarbare Kefir. Die aanvaarbaarheid van tradisioneel, MG en ander Kefirs (Candi-Kefir en Lacto-Kefir), voorberei van mikrobiologies gestabiliseerde MG, is deur 85 verbruikers geëvalueer. Die resultate het aangedui dat pH (r = 0.978; p < 0.05) 'n belangrike faktor is in die bepaling van verbruikers se voorkeur van geur is, veral by vroulike verbruikers (r = 0.978; p < 0.05). Drie groepe, elk gekenmerk deur verskillende voorkeur en aanvaarbaarheid eienskappe, is verder geïdentifiseer. Groep I het oor die algemeen van geen van die produkte gehou nie en Groep III het die effense suur Kefirs soos Candi-Kefir (7.63) en Lacto-Kefir (7.09) verkies. Groep II het die Kefir met 'n matige suurheid en hoë etanolinhoud verkies. Tradisionele Kefir het die hoogste telling (7.50) en MG Kefir die laagste telling (4.78) behaal. Die sensoriese studie is van waarde aangesien dit gelei het tot die identifisering van die drywers van verbruikersvoorkeure deur die verskillende tipes verbruikers. Tydens hierdie projek is 'n naby-infrarooi reflektansie spektroskopiese metode ontwikkel vir die vinnige skatting van melk- en asynsuur, die organise sure wat verantwoordelik is vir die suurheid van Kefir, asook die pH en titreerbare suurheid (TS). Die resultate het getoon dat die kalibrasiemodelle vir melksuur (RPD = 2.57 – 3.16), pH (RPD = 2.90) en TS (RPD = 2.60) voldoende was vir siftingsdoeleindes (2 < RPD < 3). Dit dui daarop dat hierdie modelle sal aandui wanneer die konsentrasie van melksuur, pH of TS afwissel van die normale reeks. Hierdie studie het gewys dat die geur van MG Kefir, berei van verrykte korrels, suksesvol verbeter is en het ook gelei tot insigte in die voorkeur van aanvaarbaarheid van Kefir, 'n onbekende gefermenteerde suiwelproduk vir Suid-Afrikaanse verbruikers.

Dissertation 'consists of a selection of 71 publications produced over the period 1975-2001, which were drawn from the more complete list of 198 original research papers, review articles and books published over the same period' -- declaration. / Thesis (PhD Food Sc )--Stellenbosch University, 2001. / ENGLISH ABSTRACT: One of the curious facts about the food industry is that many of the processes in use today were being practised, in some form or other, by the Roman legions as they marched across Europe and beyond. Certainly they were familiar with the basic techniques of fermentation, and much current research into fermented foods is concerned with understanding the fundamental nature of these traditional processes, and how the individual stages in a particular fermentation can be better controlled. Recent developments in the dairy industry have tended to reflect this pattern and, over the years, my research group has done much to support the expanding markets for yoghurt and similar fermented milks. Our evaluation of the polysaccharide-producing characteristics of starter cultures, for example, encouraged yoghurt manufacturers to match physical properties to the perceived demands of consumers, and most culture suppliers followed this lead by labelling their products with precise designations as to their potential for imparting viscosity to a retail item. Similarly, my group was the first to record the unique physical properties of the concentrated yoghurt, labneh, C 230 g 1-1 total solids) that had been made for hundreds of years by draining whey from natural yoghurt hanging in a cloth or animal-skin bag. This detailed analysis of the product facilitated the application of ultra-filtration to natural yoghurt to generate a product with a quality that matched traditionallabneh and, today, factories in the Middle East, Greece and elsewhere are using modern membrane-filtration plants to satisfy a growing market demand. Our success in publicising the attractive properties of concentrated yoghurt encouraged me to devote time to yet another 'historical' concept, namely the apparent 'health benefits' derived by small communities in Eastern Europe from consuming kefir and koumiss. In the West, the flavour and texture of these latter products have never been accepted, but employing similar cultures to produce 'health-promoting' bio-yoghurts opened an entirely new avenue for research. As clinical evidence in support of the prophylactic and therapeutic properties of Lactobacillus acidophilus and a species of Bifidobacterium became available, so it became apparent that the therapeutic advantage that accompanies the regular ingestion of 'bio-yoghurts' depended on the survival of these microfloras over the stipulated shelf-lives of the retail vehicles. However, no laboratory medium was immediately available for the simultaneous enumeration of Lb. acidophilus and Bifidobacterium along with the yoghurt cultures, i.e. Streptococcus thermophilus and Lactobacillus delbrueckii sub-sp. bulgaricus. Designing such a medium became a priority for one of my students, and, even today, the procedures that he derived are being used by consumer groups that monitor the performance of the major dairy companies in England. If the improved quality of yoghurts and 'bio-yoghurts' had a major impact on consumer perceptions of fermented milks, the food sector in England gradually became aware of an even more dramatic change in consumer attitudes. Thus twenty years ago, cheese meant 'Cheddar' but, following a 'deluge' of television publicity about the attractions of 'exotic' catering, housewives began demanding mozzarella and mascarpone for lavish desserts, Feta to sprinkle over salads and Halloumi to grill or fry. In turn, exporting countries like Italy, Greece and Cyprus came under intense pressure to increase supplies of top quality products. Local manufacturers soon realised, however, that there was little information available concerning the scientific basis to the procedures employed to make some of these traditional cheeses, and my research group was selected by Funding Agencies in Greece and Cyprus to act as a focus for a series of studies of Feta and Halloumi cheese. The need to eliminate pathogens from the storage brines of Feta cheese without killing the yeasts and bacteria associated with maturation became an important consideration for exporters, and one of my students exploited a novel procedure employing furocoumarins and long-wave ultra-violet light to achieve the desired selective inactivation. At present, the economics of commercial application are somewhat dubious but, as soon as cheap, synthetic, non-toxic furocoumarins become more readily available, the system may well merit re-evaluation. We did confirm, however, that the metabolic activities of the yeasts and bacteria typically isolated from storage brines are essential for flavour development in Feta cheese, and that similar microfloras are instrumental in the development of the important charactistics of traditional Halloumi cheese. In particular, a new species of lactic acid bacterium, Lactobacillus cypricasei, was isolated from samples of the traditional ovine cheese, but whether or not the species has a unique role(s) in the maturation process remains an open question. Clearly there is still much to learn but, if the activities of my reseach group have added just a little to the scientific background essential for future studies of cheese and fermented milks, then their completion will have been worthwhile. / AFRIKAANSE OPSOMMING: Een van die merkwaardigste feite omtrent die voedselindustrie is dat baie van die prosesse wat vandag gebruik word, in een of ander vorm deur die Romeinse magte gebruik is toe hulle deur Europa marsjeer het. Basiese fermentasie tegnieke was aan hulle bekend, en heelwat huidige navorsing oor gefermenteerde voedsel is gemik daarop om die fundamentele natuur van hierdie tradisionele prosesse te verstaan en hoe die individuele stappe in 'n spesifieke fermentasie beter beheer kan word. Onlangse ontwikkelinge in die suiwelindustrie reflekteer hierdie patroon, en my navorsingsgroep het oor die jare heelwat gedoen om die groeiende markte vir joghurt en soortgelyke gefermenteerde melk te ondersteun. Ons evaluasie van die polisakkariedproduserende eienskappe van suursels het byvoorbeeld joghurtvervaardigers gehelp om fisieke eienskappe daar te stel wat verbruikers tevrede sal stel. Meeste verskaffers van kulture het hierdie voorbeeld gevolg deur hul produkte so te etiketteer dat duidelik gewys word watter potensiaal dit het om viskositeit aan die finale produk te verleen. Verder was my groep die eerste om die unieke fisiese eienskappe van die gekonsentreerde joghurt, labneh (230 g 1-1 totale vastestowwe) te bepaal, wat vir honderde jare gemaak is deur die wei van natuurlike joghurt te dreineer deur dit in "n materiaal- of diervelsak te hang. "n Gedetailleerde analise van hierdie tradisionele produk het bygedra tot die gebruik van ultrafiltrasie op natuurlike joghurt om "n produk te gee met dieselfde kwaliteit as tradisionele labneh. Vandag gebruik fabrieke in die Midde Ooste, Griekeland en elders moderne membraan-filtrasie aanlegte om in die groeiende vraag na die produk te voorsien. Ons sukses met die bekendmaking van die aantreklike eienskappe van gekonsentreerde joghurt het my aangespoor om tyd te spandeer aan nog 'n sogenaamde "historiese" konsep, naamlik die skynbare gesondheidsvoordele van klein gemeenskappe in Oos-Europa wat kefir en koumiss verbruik. In die Weste is die smaak en tekstuur van hierdie produkte nooit werklik aanvaar nie, maar om soortgelyke kulture te gebruik om "gesondheidsbevorderende" bio-joghurt te produseer, het 'n hele nuwe navorsingsveld daargestel. Soos kliniese bewyse van die terapeutiese en voorkomende voordele van Lactobacillus acidophilus en 'n spesie van Bifidobacterium bekend gemaak is, het dit duidelik geword dat die terapeutiese voordele wat saamgaan met die gereelde inname van "bio-joghurts", afhang van die oorlewing van hierdie mikroflora oor die gestipuleerde rakleeftyd van die kommersiële produkte. Geen laboratorium medium was egter onmiddellik beskikbaar vir die gelyktydige telling van Lb. actdophilus en Bifldobacterium tesame met die joghurt kulture Streptococcus thermophilus en Lb. delbrueckii sub-sp. bulgaricus. Die ontwikkeling van so 'n medium het een van my studente se prioriteit geword, en selfs vandag word die prosedures wat deur hom ontwikkel is, gebruik deur verbruikersgroepe wat die optrede van groot suiwelmaatskappye in Engeland monitor. lndien die verbeterde kwaliteit van joghurts en bio-joghurts 'n groot impak gehad het op verbruikers se persepsie van gefermenteerde melk oor Wes-Europa heen, het die voedselsektor in Engeland bewus geraak van selfs 'n meer dramatiese verandering in verbruikers se houding. Twintig jaar terug het kaas "Cheddar" beteken, maar na 'n stortvloed televisie advertensies oor die aanloklikheid van eksotiese geregte, het daar by huisvroue 'n vraag ontstaan na Mozzarella en Mascarpone vir nageregte, Feta oor slaai en Halloumi om te bak of te braai. Italië, Griekeland en Siprus wat hierdie produkte uitgevoer het, het onder kwaai druk gekom om groter hoeveelhede, top-kwaliteit produkte te lewer. Plaaslike vervaardigers het gou agtergekom dat min inligting beskikbaar was oor die wetenskaplike basis van die prosedures wat gebruik word om hierdie tradisionele kase te maak en my navorsingsgroep is deur befondsingsagentskappe in Griekeland en Siprus genader om studies te doen oor sekere aspekte van die vervaardiging van Feta en Halloumi kaas. Dit het vir beide in- en uitvoerders belangrik geword om die patogene te elimineer uit die soutoplossing waarin Fetakaas gestoor word, sonder om die giste en bakterieë wat rypwording aanhelp, te dood. Een van my studente het 'n innoverende prosedure ontwikkel wat furocoumarins en lang-golf-ultra-violet lig gebruik om selektiewe inaktivering te kry. Op die oomblik is daar effense onsekerheid oor die ekonomiese implikasies van die kommersiële toepassing, maar sodra goedkoop, sintetiese, nie-toksiese furocoumarins geredelik beskikbaar word, moet die sisteem weer geëvalueer word. Ons het egter bevestig dat die metaboliese aktiwiteite van die giste en bakterieë in die stooroplossing noodsaaklik is vir geurontwikkeling in Feta kaas en dat soortgelyke mikrofloras instrumenteel is in die ontwikkeling van die belangrike karaktereienskappe van tradisionele Halloumi kaas. 'n Unieke melksuurbakterium, Lactobacillus cypricasei, is uit monsters tradisionele skaap Halloumi geïsoleer, maar of hierdie spesie 'n unieke rol speel in die verouderingsproses is nog 'n ope vraag. Duidelik is daar nog baie om te leer, maar indien my navorsingsgroep se aktiwiteite slegs 'n klein bydrae gemaak het tot die wetenskaplike agtergrond wat essensieel is vir toekomstige navorsing, was die voltooiing daarvan die moeite werd.