Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The potential malting, brewing and antiyeast characteristics of twelve selected sorghum cultivars from Zambia (MMSH 375, 625, 707, 1038, 1077, 1194, 1257, 1356, 1363, 1365, 1376 and 1401) was evaluated. This was done through the determination of tannin content, proximate composition, %germinative energy (%GE), micro-structure, diastatic power (DP) and free amino nitrogen (FAN); as well as the antiyeast activity of N-containing compounds for each cultivar. All cultivars were tannin-free and thus suitable for brewing potential exploration. Seven cultivars (MMSH-375, 625, 1038, 1194, 1257, 1401 and 1376) had a %GE considered appropriate for malting and brewing. A maximum of 25% of the DP level recommended for commercial malting was achieved in this study. In spite of the low DP observed in all cultivars after malting, high extract levels ranging between 18.7 and 25.5˚P were achieved. In unmalted grains a significantly FAN level (p≤0.05) was observed in three cultivars (MMSH-375, 1194 and 1077). These FAN values, however, represented less than 10% of the recommended FAN level necessary to support proper yeast functioning during wort fermentation. The 150 mg/L threshold which is necessary to support proper yeast function and is employed in modern day brewing was achieved in malts of sorghum cultivars MMSH-375 (intermediate cultivar) and 1401 (intermediate cultivar). A FAN level between 100 and 140 mg/L, which is considered enough to support optimal fermentation, was achieved in cultivars MMSH-625 (intermediate cultivar), 1077 (hard cultivar), 1194 (intermediate cultivar), 1356 (soft cultivar) and 1376 (intermediate cultivar) after malting. Mashing did not significantly increase FAN levels in all sorghum cultivars. The addition of potassium metabisulphite (KMS) in the mash did, however, lead to a further increase of FAN levels in all cultivars. Scanning electron micrographs revealed that the corneous endosperm was inaccessible to degradation by enzymes and only the soft endosperm was modified in all cultivars during malting. The N-containing compounds from selected malts of sorghum cultivars with good malting and brewing potential (MMSH-375, 625, 1401 and 1194) were isolated and their antiyeast activity was determined. It was found that the N-containing compounds were playing an essential role during fermentation by contributing positively towards yeast growth in all four cultivars. However, a 20-30% reduced growth at the lower concentrations of the putative %yeast growth promoting N-containing compounds was observed in all cultivars. Irrespective of the reduced %yeast growth observed in all four cultivars at low concentrations of the putative yeast growth N-containing compounds, it could not be concluded that the sorghum cultivars utilised in this study possess antimicrobial peptides and proteins because only small compounds (<1 kDa) were detected with UPLC-MS. The dose-response data showed that extracts of MMSH-375 and MMSH-625 resulted in generally a higher %yeast growth when compared to other cultivars. The UPLC-MS also confirmed the dose response data that MMSH-375 has a better qualitative yeast-feeding value. MMSH-375 is thus rated as the best cultivar out of the four that were screened and is recommended to be use in the commercial production of sorghum lager beer. / AFRIKAANSE OPSOMMING: Die potensiële mout, brou en teen-gis eienskappe van twaalf geselekteerde Zambiese sorghum kultivars (MMSH 375, 625, 707, 1038, 1077, 1194, 1257, 1356, 1363, 1365, 1376 en 1401) was geëvalueer. Dit is gedoen deur die bepaling van tannien inhoud, proksimale samestelling, % ontkiemings energie (%OE), mikrostruktuur, diastatiese krag (DK) en vrye amino stikstof (VAS) inhoud; sowel as die teen-gis aktiwiteit van stikstofbevattende verbindings vir elke kultivar. Alle kultivars was tannien vry en dus geskik om te ondersoek vir brou potensiaal. Sewe kultivars (MMSH 375, 625, 1038, 1194, 1257, 1401 en 1376) het ‘n %OE geskik vir mouting en brouery gehad. ‘n Maksimum van 25% van die voorgestelde DK vlak vir kommersiële brouery was gevind in hierdie studie. Hoë ekstrak vlakke van tussen 18.7 en 25.5˚P is gevind, ten spyte van die lae DK wat gevind is in alle kultivars na mouting. ‘n Betekenisvolle VAS vlak (p≤0.05) was gevind in die ongemoute graankorrels van drie kultivars (MMSH 375, 1194 en 1077). Hierdie VAS vlakke was egter minder as 10% van die voorgestelde VAS vlakke benodig om gis funksie te ondersteun tydens fermentasie. Die 150 mg/L drumpelwaarde benodig vir korrekte gis funksie en gebruik in moderne brouery is bereik in gemoute sorghum kultivars MMSH 375 (intermediêre kultivar) en 1401 (intermediêre kultivar). ‘n VAS vlak van tussen 100 en 140 mg/L, gereken as genoegsaam vir optimal fermentasie, was bereik in kultivar MMSH 625 (intermediêre kultivar), 1077 (harde kultivar), 1194 (intermediêre kultivar), 1356 (sagte kultivar) en 1376 (intermediêre kultivar) na mouting. Warm water weking het nie die VAS vlakke in die sorghum kultivars betekenisvol verhoog nie. Die byvoeging van kalium metabisulfiet (KMS) tot die weekvloeistof het egter gelei tot ‘n verdere verhoging van VAS vlakke in alle kultivars. Skandering elektronmikrograwe het aangedui dat die growwe endosperm ontoeganklik is vir ensiematiese afbraak en dat slegs die sagte endosperm van alle kultivars veranderinge ondergaan het tydens mouting. Die stikstofbevattende verbindings van die gemoute sorghum kultivars geselekteer op grond van hul goeie mout en brou potensiaal (MMSH 375, 625, 1401 en 1194) was geïsoleer en hul teen-gis aktiwiteit was bepaal. Daar was bevind dat die stikstofbevattende verbindings ‘n noodsaaklike rol speel tydens fermentasie deur ‘n positiewe bydrae tot gisgroei te maak in al vier kultivars. Verminderde groei (20-30%) was egter opgelet by laer konsentrasies van die vermeende groei-bevorderende stikstofbevattende verbindings in alle kultivars. Ten spyte van hierdie verminderde gisgroei by lae konsentrasies kon daar nie afgelei word dat die sorghum kultivars gebruik in hierdie studie wel antimikrobiese peptiede en proteïne bevat nie aangesien slegs klein verbindings (<1 kDa) waargeneem word met UPLC-MS. Die dosis-respons data het aangedui dat ekstrakte van MMSH 375 en 625 oor die algemeen gelei het tot hoër gisgroei in vergelyking met ander kultivars. UPLC-MS het ook bevestig dat MMSH 375 ‘n beter kwalitatiewe gisvoedingswaarde het. MMSH 375 word dus gereken as die beste kultivar uit die vier gekeurde kultivars en word aanbeveel vir gebruik in die kommersiële produksie van sorghum lager bier.

Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Perforation-mediated modified atmosphere packaging (PM-MAP) offers the possibility of optimising polymeric films in order to compensate for barrier limitations of conventional modified atmosphere packaging (MAP). The aim of this study was to investigate the effects of PM-MAP and storage duration on the physico-chemical quality attributes, microbial quality, phytochemicals (anthocyanins, phenolics and ascorbic acid) and antioxidant activities of arils from fresh minimally processed pomegranate (cv. Acco). The effects of number of perforations (0, 3, 6 and 9; Ø = 0.8 mm) and storage temperature (5, 10 and 15 ºC) on water vapour transmission rate (WVTR, g/m2.day) of synthetic ‘Polylid’ and biodegradable (Nature flexTM) polymeric films were investigated. The results showed that non-perforated biodegradable film had higher WVTR at all storage temperatures, and irrespective of film type, increasing the number of perforations (from P-3 to P-9) had higher impact on WVTR than increasing storage temperature (from 5 to 15 ºC). Furthermore, this study investigated the effects of PM-MAP on the physico-chemical properties, phytochemicals components and antioxidant activities of fresh minimally processed arils. Arils (100 g) were packaged in polypropylene trays (10.6 x 15.1 cm2) and heat-sealed with a polymeric film POLYLID®. Perforations (0, 3, 6 and 9; Ø = 0.8 mm) were made on the top of the film and all samples were stored at 5 ± 1 ºC and 95 ± 2% relative humidity for 14 days. Samples were analysed at intervals of 3, 6, 9, 12 and 15 days. Microbial analysis included tests for Escherichia coli, aerobic mesophilic bacteria, yeast and moulds at days 0, 6, 10 and 14. The results showed that headspace gas composition was significantly influenced by the number of perforations, which helped balance the decrease in O2 with corresponding increase in CO2 levels, thus preventing anoxic conditions. Total soluble solids, titratable acidity and firmness of arils were slightly reduced by PM-MAP compared to clamshell trays. Colour attributes was generally maintained across all treatments and throughout the storage duration. The highest counts of aerobic mesophilic bacteria (5.5 log CFU/g), yeast and moulds (5.3 log CFU/g) were observed in P-0 and P-9 packages, respectively. Overall, P-3 and P-6 better maintained the physico-chemical properties and microbial quality of arils. Total phenolics and anthocyanin contents were higher in arils packaged in PM-MAP while ascorbic acid was slightly reduced. Antioxidant activities tested against FRAP and DPPH radical-scavenging activity increased across all types of MAP over storage duration. However, antioxidant activities were significantly higher in pomegranate arils packaged in PM-MAP due to O2-promoted biosynthesis of phenolics and anthocyanins which constitute the antioxidant properties. Overall, the results reported in this study showed that the use of PM-MAP in cold chain could be suitable for the preservation of physico-chemical quality, phytochemical contents and antioxidant properties of arils packaged in passive PM-MAP compared to clamshell and non-perforated packages during postharvest handling and storage. Perforating MAP films showed potential in preventing the incidence of in-package moisture condensation which is a common problem during postharvest handling and storage of fresh produce packaged inside non-perforated MAP. The results also showed the importance of keeping PM-MAP packs in closed refrigerated shelves to avoid cross contamination or ingress of foodborne pathogens. / AFRIKAANSE OPSOMMING: Perforasie-bemiddelde gewysigde-verpakking (PM-MAP) maak dit moontlik om polimeer films te optimiseer en om sodoende te kompenseer vir die versperring beperkings van die konvensioneel-gewysigde atmosfeer verpakking (MAP). Die doelwit is om die effek van PM-MAP en die duur van stoor op die fisioko-chemiese gehalte kenmerke, mikrobiale gehalte, fitochemikale (antisianien, fenolies en askorbiensuur) en antioksidant aktiwiteite van granaatarils van vars, minimaal geprosesseerde granate, te ondersoek (cv. Acco). Die effek van die aantal perforasies (0, 3, 6 en 9; Ø =0.8 mm) en stoortemperatuur (5, 10 en 15 ºC) op die waterdamp transmissie koers (WVTR, g/m2.day) van sintetiese ‘Polylid’ en biodegradeerbare (Nature flexTM) polymeriese films is ondersoek. Die resultate het bewys dat nie-perforeerde biodegradeerbare film by alle stoortemperature ’n hoër WVTR het, en dat by alle tipes film, ’n verhoogde aantal perforasies (van P-3 tot P-9) ’n hoër impak op WVTR het as ’n verhoogde stoortemperatuur (van 5 tot 15 ºC). Verder is die effek van PM-MAP op die fisiko-chemiese kenmerke, fitochemikale komponente en antioksidant aktiwiteite van vars, minimaal-geprosesseerde granaatarils bestudeer. Die granaatarils (100 g) is verpak in in polipropilien (PP) platkissies (10.6 x 15.1 cm2) en verseël met polimeer film, POLYLID®. Perforasies (0, 3, 6 en 9; Ø =0.8 mm) is aan die bo-end van die film aangebring en alle voorbeelde is vir 14 dae teen 5 ± 1 ºC en 95 ± 2 % relatiewe humiditeit. Die voorbeelde is met tussenposes van 3, 6, 9, 12 en 15 dae ontleed. Die ontleding het toetse vir Escherichia coli, aerobiese mesofiliese bakterië, suurdeeg en skimmel op tussernposes van 0, 6, 10 en 14 dae ingesluit. Die resultate bewys dat die komposisie van die gas beïnvloed word deur die aantal perforasies. Dit help om die vermindering in O2 met ’n ooreenkomstige toename in CO2 vlakke te balanseer en om dus toestande wat deur ’n gebrek aan suurstof veroorsaak is, te verhoed. Die totaal van oplosbare vaste stowwe, titreerbare suurgehalte en fermheid van die granaatarils is deur die PM-MAP verminder veral as dit vergelyk word met “clamshell trays”. Die kleur kenmerke het oor die algemeen dieselfde gebly by al die behandelings en dwarsdeur die stoortydperk. Die hoogste aantal aerobiese mesofiliese bakterië (5.5 log CFU/g), gis en skimmel (5.3 log CFU/g) is in die P-0 en P-9 verpakkings onderskeidelik opgemerk. Oor die algemeen is P-3 en P-6 beter in staat om die fisioko-chemiese kenmerke en mikrobiale gehalte van die granaatarils te behou. Die totaal van die fenoliese and antosianiin inhoud was hoër in granaatarils wat verpak is in PM-MAP maar die askorbiensuur was effens laer. Antioksdant aktiwiteite is getoets teen FRAP en DPPH aktiwiteite het by al die tipes van MAP tydens stoor vermeerder. Antioksidant aktiwiteite was egter heelwat hoër in granate wat in PM-MAP verpak is. Dit is die gevolg van die biosintese van fenolies en antosianins wat deur O2 in die hand gewerk word en wat die basis van antioksidant kenmerke vorm. Oor die algemeen toon die resultate van hierdie studie dat die gebruik van PM-MAP in die koue ketting geskik is vir die behoud van fisieko-chemiese gehalte, fitochemiese inhoud en antioksidant kenmerke van granaatarils wat in passiewe MAP verpak is, veral as dit vergelyk word met die vrugte wat in ‘clamshell’ en nie-geperforeerde verpakking tydens hantering na die oes en tydens stoor verpak is. Die perforeer van MAP films kan die voorkoms van die kondensasie in die verpakking verminder. Hierdie kondensasie is ’n algemene probleem tydens die hantering en stoor van vars vrugte wat in MAP sonder gaatjies verpak is. Die resultate toon ook hoe belangrik dit is om die PM-MAP verpakking in toe, verkoelde rakke te hou en om sodoende kruis-kontaminasie asook kontaminasie deur kieme wat in vrugte teenwoordig is, te voorkom.

Thesis (PhD (Food Science))--University of Stellenbosch, 2007. / Thermal pasteurisation failures in the dairy industry have often been found to cause end-products of poor quality and short shelf-life. Therefore, alternative methods to eliminate microbial contaminants in raw milk are being studied. Ultrasonication is one such non-thermal technology that could offer the dairy industry an alternative to traditional pasteurisation. The main objective of this dissertation was to evaluate the use of high-power lowfrequency ultrasound (20 kHz, 750 W, 124 μm) applied in batch mode to eliminate a selection of spoilage and potentially pathogenic microbes, commonly associated with milk. These included Gram-positive and negative microbes, comprising of rods and cocci, an endospore-former, and a yeast (Escherichia coli, Bacillus cereus, Chryseobacterium meningosepticum, Lactobacillus acidophilus, Lactococcus lactis, Listeria monocytogenes, Micrococcus luteus, Pseudomonas fluorescens and Saccharomyces cerevisiae). Three strains of E. coli (1 x 106 cfu.ml-1) tested, viz. ATCC 11775, a wild strain from raw milk, and an O157:H7 strain from milk were sensitive to ultrasonication. Complete elimination of viable cells occurred within 10 min. Viable counts of P. fluorescens were reduced by 100% within 6 min of ultrasonication and L. monocytogenes was reduced by 99.0% within 10 min. Lactococcus lactis was reduced by 97.0% and M. luteus, B. cereus and C. meningosepticum by 88.0%, 87.0% and 85.0% respectively. Lactobacillus acidophilus showed the most resistance to ultrasound with only 78.0% of viable cells being eliminated. Under similar conditions, S. cerevisiae was reduced by 99.7%. Microbial cell morphology, size and Gram status did not necessarily influence the efficacy of ultrasonication. Sterile saline solution and UHT milk were used as the suspension media, and the reputed protective effect of milk fat was not observed under the parameters used in this study. A higher wave amplitude (100%; 124 μm) was found to be more efficient in eliminating microbes than a lower wave amplitude (50%; 62 μm). Pulsed-ultrasonication did not enhance the efficiency of ultrasonication indicating that standing waves were absent. Limited success was achieved by ultrasonication itself, and the long batch treatment time (10 min or more) was found to be unrealistic for industrial implementation. Hence the simultaneous application of ultrasound and heat (thermoultrasonication) was examined. Thermo-ultrasonication proved to be more effective than either an ultrasonic or heat treatment with all viable M. luteus cells being eliminated within 4 min (100% amplitude at 72°C). Similarly, to eliminate E. coli and Lb. acidophilus from milk, only 2 min and 4 min thermo-ultrasonication was required, respectively. Bacillus cereus endospores remained resistant and after a 10 min thermo-ultrasonic treatment only 78.04% were eliminated. During this investigation both extensive surface (SEM) and internal (TEM) cell damage caused by ultrasonication were observed in E. coli, Lb. acidophilus and S. cerevisiae. Hence ultrasonication physically/mechanically damages these microbial cells causing cell death/injury. Microbial proteins and DNA released from cells into the environment after an ultrasonic treatment was measured and an increase in released microbial proteins and DNA was found to be indicative of a decrease in the number of viable cells, providing that the initial cell concentration was high enough. It was, however, not possible to correlate the concentration of released microbial proteins and DNA with the exact number of viable cells eliminated, rendering it an ineffective quality indicator for the industry. Ultrasonication had no statistically significant influence on the protein, fat and lactose content of both raw and pasteurised milk. The somatic cell count of raw and pasteurised milk was found to decrease after ultrasonication. Unlike with heating, activity of alkaline phosphatase and lactoperoxidase were not reduced by ultrasonication. Hence neither enzyme can be used to indicate a successful ultrasonic treatment of milk. This study has demonstrated that ultrasonication offers a viable alternative to pasteurisation as it is effective in eliminating microbes, and does not alter native milk components. However, to attain a more effective killing, thermo-ultrasonication is recommended for the treatment of milk to be used for the production of different dairy products.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Maize (Zea mays L.) is used for human and animal consumption in diverse forms, from specialised foods in developed countries, to staple food in developing countries. Unfortunately, maize is prone to infection by different Fusarium species that can produce harmful mycotoxins. Fusarium verticillioides is capable of asymptomatic infection, where infected kernels show no sign of fungal growth, but are contaminated with mycotoxins. If fungal contamination is not detected early on, mycotoxins can enter the food chain. Rapid and accurate methods are required to detect, identify and distinguish between pathogens to enable swift decisions regarding the fate of a batch or consignment of cereal. Near infrared (NIR) hyperspectral imaging and multivariate image analysis (MIA) were evaluated to investigate the fungal development in maize kernels over time. When plotting principal component (PC) 4 against PC5, with percentages sum of squares (%SS) 0.49% and 0.34%, three distinct clusters were apparent in the score plot and this was associated with degree of infection. Prominent peaks at 1900 nm and 2136 nm confirmed that the source of variation was due to changes in starch and protein. Variable importance plots (VIP) confirmed the peaks observed in the PCA loading line plots. Early detection of fungal contamination and activity (20 h after inoculation) was possible before visual symptoms of infection appeared. Using NIR hyperspectral imaging and MIA it was possible to differentiate between species of Fusarium associated with maize. It was additionally applied to examine the fungal growth kinetics on culture media. Partial least squares discriminant analysis (PLS-DA) prediction results showed that it was possible to discriminate between species, with F. verticillioides the least correctly predicted (between 16-47% pixels correctly predicted). For F. subglutinans 78-100% and for F. proliferatum 60-80% pixels were correctly predicted. Three prominent bands at 1166, 1380 and 1918 nm were considered to be responsible for the differences between the growth zones. Variations in the bands at 1166 and 1380 nm were correlated with the depletion of carbohydrates as the fungus grew while the band at 1918 nm was a possible indication of spore and new mycelial formation. By plotting the pixels from the individual growth zones as a function of time, it was possible to visualise the emergence and interaction of the growth zones as separate growth profiles. The microstructure of fungal infected maize kernels was studied over time using high resolution X-ray micro-computed tomography (μCT). The presence of voids and airspaces could be seen in two dimensional (2D) X-ray transmission images and in the three dimensional (3D) tomograms. Clear differences were detected between kernels imaged after 20 and 596 h of inoculation. This difference in voids as the fungus progressed showed the effect of fungal damage on the microstructure of the maize kernels. Imaging techniques are important for rapid, accurate and objective evaluation of products for quality and safety. NIR hyperspectral imaging offers rapid chemical evaluation of samples in 2D images while μCT offers 3D microstructural information. By combining these image techniques more value was added and this led to a comprehensive evaluation of Fusarium infection in maize. / AFRIKAANSE OPSOMMING: Mielies (Zea mays L.) word in verskeie vorms deur mens en dier verbruik, van gespesialiseerde voedsel in ontwikkelde lande, tot stapelvoedsel in ontwikkelende lande. Ongelukkig is mielies onderhewig aan besmetting deur verskeie Fusarium spesies wat skadelike mikotoksiene kan produseer. Fusarium verticilloioides is in staat tot asimptomatiese infeksie waar die besmette pit geen teken van fungusgroei toon nie, maar (reeds) met mikotoksiene besmet is. Indien fungusbesmetting nie vroegtydig opgespoor word nie, kan mikotoksiene die voedselketting betree. Vinnige en akkurate metodes word benodig om patogene op te spoor, te identifiseer en ook om onderskeid tussen patogene te tref om sodoende (effektiewe) besluite aangaande die gebruik van ‘n lot of besending graan te neem. Naby-infrarooi (NIR) hiperspektrale beelding en meerveranderlike beeld ontleding (MIA) is geëvalueer om fungusontwikkeling in mieliepitte oor tyd te ondersoek. Wanneer hoofkomponent (PC) 4 teenoor PC5 gestip word, met persentasies som van kwadrate (%SS) 0.49% en 0/34%, is drie afsonderlike groepein die telling grafiek waargeneem. Dit is geassosieer met die graad van besmetting. Prominente pieke by 1900 nm en 2136 nm het bevestig dat veranderinge in stysel en proteïene die bron van die variasie was. Veranderlike belangrikheidsgrafieke (VIP) het die pieke wat in die PCA beladingslyngrafieke waargeneem is, bevestig. Vroegtydige opsporing (bespeuring) van fungusbesmetting en aktiwiteit (20 h na inokulasie) was moontlik voor visuele besmettingsimptome verskyn het. Onderskeid tussen Fusarium spesies wat met mielies geassosieer word, was moontlik deur gebruik te maak van NIR hiperspektrale beelding en MIA. Dit is bykomend toegepas om fungusgroeikinetika op kwekingsmedia te bestudeer. Parsiële kleinste kwadrate diskriminantanalise (PLS-DA) voorspellingsresultate het getoon dat dit moontlik was om tussen spesies te onderskei, met F. verticillioides die minste korrek voorspel (tussen 19-47% beeldelemente korrek voorspel). Vir F. subglutinans is 78-100% en vir F. proliferatum is 60-80% beeldelemente korrek voorspel. Drie prominente bande by 1166, 1380 en 1918 nm is oorweeg as oorsaak vir die verskille tussen die groeisones. Variasies in die bande by 1166 en 1380 nm is gekorreleer met die vermindering van koolhidrate soos die fungus groei, terwyl die band by 1918 nm ‘n moontlike aanduiding van spoor en nuwe miseliale vorming is. Deur die beeldelemente van die individuele groeisones as ‘n funksie van tyd te stip, was dit moontlik om die verskyning en interaksie van die groeisones as aparte groeiprofiele te visualiseer. Hoë-resolusie X-straal mikro-berekende tomografie (μCT) is gebruik om die mikrostruktuur van fungusbesmette mieliepitte oor tyd te ondersoek. Die voorkoms van leemtes en lugruimtes kon in die twee-dimensionele (2D) X-straal transmissie beelde en in die drie-dimensionele (3D) tomogramme gesien word. Duidelike verskille is waargeneem tussen pitte wat na 20 en 596 h na inokulasie verbeeld is. Hierdie verskil in leemtes soos die fungus vorder, het die effek van fungusskade op die mikrostruktuur van mieliepitte getoon. Beeldingstegnieke is belangrik vir vinnige, akkurate en objektiewe evaluasie van produkte vir kwaliteit en veiligheid. NIR hiperspektrale beelding bied vinnige chemiese evaluering van monsters in 2D beelde, terwyl μCT 3D mikrostrukturele inligting gee. Meer waarde is toegevoeg deur hierdie beeldingstegnieke te kombineer en dit het gelei tot ‘n omvangryke evaluering van Fusarium besmetting in mielies.

Thesis (PhD (Food Sc))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Ostrich meat has become increasingly popular in South Africa and abroad, driven by the health conscious trend and ostrich meat’s natural low intramuscular fat, high polyunsaturated fatty acid and low cholesterol content. This increased demand led to the investigation of novel packaging regimes to improve its attractiveness and shelf-life. Different modified atmospheric packaging regimes were studied for fresh and frozenthawed ostrich M.iIliofibularis steaks stored at ±4°C for 10 days. Oxygen MAP (30 CO2:70 O2) was applied with great success to fresh steaks, and resulted in significantly improved colour stability, decreased drip loss and a 10-day shelf-life. Oxygen MAP of frozen-thawed ostrich steaks was not successful as the colour deteriorated within 3 days, coupled with high lipid and protein oxidation. The microbial shelf-life was not influenced by freezing and thawing. The use of nitrogen MAP (30 CO2:70 N2) as an alternative to vacuum packaging for fresh and frozen-thawed ostrich meat was inconclusive due to trace amounts of residual oxygen in the headspace accelerating myoglobin oxidation by depleting the metmyoglobin reducing activity. The differences in oxidative stability of the fresh and frozen-thawed ostrich meat led to the investigation of the source of these differences and a system that would allow control over the freezing and thawing practice. This was supported by the industry that is under increasing pressure to reduce the excessive (15-20%) thaw weight loss that is continually reported. Subsequently, a mathematical prediction model based on the control volume approach was developed that predicted the rate of freezing and thawing of intact whole vacuum-packed ostrich muscle. The model predicted with greater accuracy than existing models, and can be used successfully by the industry to optimally design, control and operate their systems. Furthermore research was conducted to investigate the effect of different freezing and thawing rates on the ice crystal formation and the quality of ostrich M. femorotibialis stored at ±4°C post freeze/thaw. Five characteristic freezing rates (FR (time from 0°C to -7°C): 1, 2, 4, 8, 24h) were paired with five characteristic thawing rates (TR (time form -7°C to 0°C): 1.5, 3, 6.5, 14, 21h) in a completely randomised block design. Results showed that thawing had no impact on any of the tested quality parameters, including thaw loss. Freezing rate however did influence the ice crystal formation and at a characteristic freezing rate of one hour (FR_1h) only intracellular ice crystals were observed throughout the M. femorotibialis leading to the lowest thaw loss (2.57%) and highest shear force. Freezing rate of 2h, 4h and 8h (FR_2h, FR_4h and FR_8h) were dominated by extracellular ice crystals. FR_2h and FR_8h showed major dehydration of the muscle fibres and excessive distortion of the muscle fibre matrix that led to significantly lower oxidative stability. FR_24h (approximately commercial rates) formed columns of ice from the surface to the centre of the meat resulting in the highest thaw loss (6.24%). FR_4h was judged to deliver the best quality product with moderate thaw (3.93%) and drip loss, low cooking loss, good colour stability and extremely low TBARS. FR_4h is an achievable rate of freezing for the industry and if implemented should decrease the thaw loss problem as well as increase revenue and throughput in the processing facility. / AFRIKAANSE OPSOMMING: ‘n Hedendaagse strewe na ‘n gesonde lewenstyl tesame met die natuurlike lae vetinhoud (d.i. hoë poli-onversadigde vetsure en lae cholesterolvlak) van volstruisvleis het gelei tot ‘n toename in die nasionale en internasionale aanvraag. Hierdie het ook die behoefte laat ontstaan om nuwe verpakkingstegnieke te ondersoek om sodoende die aanvaarbaarheid en rakleeftyd van die produk te verleng. Die invloed van verskeie gewysigde atmosferiese verpakkingsmetodes (GAV) op die kleurstabiliteit, drupverlies en rakleeftyd van vars en bevrore/ontdooide volstruisvleis (spesifiek M. Iliofibularis), gestoor by ±4°C vir 10 dae, is ondersoek. Die suurstof GAV (30 CO2:70 O2) van vars volstruisvleis het ‘n verbetering in kleurstabiliteit, verlaagde drupverlies en 'n verlengde mikrobiese rakleeftyd (10 dae) tot gevolg gehad. Die suurstof GAV van bevrore-ontdooide volstruisvleis het geen voordelige effek op kleurstabiliteit en rakleeftyd getoon nie. Die bevrore/ontdooide monsters het totaal verkleur na 3 dae en ‘n hoë vlak van lipied- en proteïenoksidasie is waargeneem. Die bevriesing en ontdooiing het geen invloed op rakleeftyd gehad nie. Die moontlikheid om stikstof GAV (30 CO2:70 N2) as 'n alternatief tot vakuumverpakking vir vars en bevrore/ontdooide volstruisvleis te gebruik, is beïnvloed deur die teenwoordigheid van oorblywende suurstof in die lugruimte van die GAV, met ‘n gevolglike toename in die tempo van mioglobien oksidasie as gevolg van ‘n afname in die metmioglobien reduksie aktiwiteit. Die verskil in die oksidatiewe stabiliteit van vars en bevrore/ontdooide volstruisvleis het gelei tot ‘n verdere ondersoek na die oorsaak van die verskille en die ontwikkeling van ‘n moontlike protokol om die oksidatiewe stabiliteit en dus rakleeftyd van volstruisvleis, te verbeter en bestuur. Die behoefte aan so ‘n protokol is beklemtoon deur die bedryf wat onder toenemende druk verkeer om buitensporige ontdooiingsverliese (15-20%) te verminder. ‘n Wiskundige voorspellingsmodel, gebaseer op die beheer-volume benadering, is ontwikkel om die tempo van bevriesing en ontdooiing van vakuumverpakte heel volstruisspiere te voorspel. Die model het tempo van bevriesing en ontdooiing met groter akkuraatheid as die bestaande modelle voorspel en kan suksesvol gebruik word in die bestuur van slagpale. Verder navorsing is onderneem om ondersoek in te stel na die effek van die tempo van bevriesing en ontdooiing op die kwaliteit van die bevrore-ontdooide volstruisvleis tydens berging by ±4°C. Die invloed van die kombinasie van vyf bevriesingstempo’s (FR (tydsverloop 0°C tot -7°C): 1, 2, 4, 8, 24 h) met vyf ontdooiingstempo’s (OT (tydsverloop -7°C to 0°C): 1.5, 3, 6.5, 14, 21 h) is ondersoek. Die resultate het getoon dat ontdooiingstempo geen beduidende invloed op enige van die kwaliteit kriteria, insluitend ontdooiingsverlies, gehad het nie. Bevriesingtempo het egter ‘n groot rol ten opsigte van yskristalvorming gespeel. Teen ‘n kenmerkende bevriesingstempo van een uur (FR_1h) was slegs intrasellulêre yskristalle waargeneem dwarsdeur die M. femorotibialis wat gelei het tot die laagste ontdooiingsverlies (2.57 %). Die ander bevriesingstempo’s, d.i. FR_2h, FR_4h en FR_8h, het gelei tot die vorming van meestal ekstrasellulêre yskristalle. Bevriesingstempo’s van FR_2h en FR_8h het beduidende dehidrasie van die spiervesels en vervorming van die spiervesel matriks tot gevolg gehad, wat tot verhoogde oksidasie gelei het. ‘n Bevriesingstempo van FR_24h (d.i. kommersieële tempo), het gelei tot die vorming van yskolomme van die oppervlak na die middelpunt van die spier, wat gevolglik die grootste ontdooiingsverlies (6.24%) tot gevolg gehad het. ‘n Bevriesingstempo van vier ure (FR_4h) is bestempel as die mees geskikte bevriesings tempo as gevolg van ‘n matige ontdooiingsverlies (3.93%), drupverlies, lae kookverlies, goeie kleur stabiliteit en uiters lae lipiedoksidasie te verseker. Die FR_4h bevriesingstempo is haalbare in die bedryf. Indien dit geïmplementeer word, sal dit waarskynlik die deurset van die slagpalesiklus asook die kostedoeltreffendheid van die volstruisbedryf vebeter, deur die vermindering van ontdooiingsverlies en verbetering van die algehele kwalitiet van die vleis.

Thesis (PhD (Food Sc))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The wildlife industry in Namibia has shown tremendous growth over the past decades and is currently the only extensive production system in Namibia that is expanding. Harvesting game for the purpose of meat production is a viable option since there is a worldwide demand for healthy and high quality proteins. The main objective of the dissertation was to investigate selected parameters required to develop a sustainable Namibian game meat industry. The major species suitable for commercial harvesting operations are springbok (Antidorcas marsupialis – Zimmerman, 1780), gemsbok (Oryx gazella – Linnaeus, 1785), kudu (Tragelaphus strepsiceros – Pallas, 1766), mountain zebra (Equus zebra hartmannae – Linnaeus, 1758) and red hartebeest (Alcelaphus buselaphus caama – Pallas, 1766). Eland (Tragelaphus oryx – Pallas, 1766) could be considered as a suitable species, although the numbers of animals that can be harvested during an operation are limited. This study demonstrated that gender influenced live weight of springbok, kudu and red hartebeest. Gender also influenced carcass weights for springbok, gemsbok, kudu and red hartebeest, but not for eland, while dressing percentage did not differ between gender for springbok, gemsbok, kudu and red hartebeest. Although there were some statistical differences in the chemical composition of the various muscles from the different species (Mm. biceps femoris, infraspinatus, longissimus dorsi, semimembranosus, semitendinosus and supraspinatus), it is doubtful whether consumers would be able to distinguish between these. Discriminant analysis could not differentiate among the different muscle groups for springbok and gemsbok. A differentiation was, however, revealed among the various muscles for red hartebeest. During the investigation on the influence of season and gender on the carcass yields and meat quality characteristics of kudu and red hartebeest, dressing percentage was affected by season, but not by gender. Muscle colour differed significantly between seasons. Results from this study showed that male eland contained more saturated fatty acids than females, but no gender differences were observed for polyunsaturated fatty acids. Hides of gemsbok, kudu and red hartebeest contributed 6 – 7% of live weight, while the skin of springbok contributed 4 – 5% of live weight. Comparisons of offal items among species showed significant differences for all offal items, except for intestines. Retail cuts showed significant species difference for rump, topside, silverside and sinews. No significant species differences were observed for thick flank and bolo. Significant gender differences were observed for silverside. No interactions between species and gender were found for the different retail cuts from gemsbok and kudu. Microbiological counts of game meat, chilled for 6 weeks and frozen for 12 months, respectively, were found to be within acceptable limits as prescribed by the South African retail market. Differences in physico-chemical and microbiological properties were observed among salami from different game species. The springbok salami was found to be microbiologically unstable. The main characteristics observed while tasting the salami from springbok, gemsbok, kudu and zebra were a distinctive smoky, salty, pepper and salami flavour combined with a smoky, salami aroma. Game flavour did not feature as strong during the sensory analyses. Sustainable utilization of game for commercial meat production has the potential to increase earnings to beneficiaries in the wildlife sector. Results from this study contributed knowledge which can be utilized to develop the Namibian game meat industry. / AFRIKAANSE OPSOMMING: Die wildsbedryf in Namibië het die afgelope dekades buitengewone groei getoon en is huidiglik die enigste ekstensiewe produksie-sisteem wat in Namibië uitbrei. Die oes van wild is ʼn voordelige opsie, aangesien daar wêreldwyd ʼn aanvraag is na gesonde en hoë kwaliteit proteïene. Die hoofdoelwit van hierdie dissertasie was die loods van ʼn ondersoek na geselekteerde aspekte wat benodig word om die Namibiese wildsvleisbedryf te ontwikkel. Die belangrikste spesies geïdentifiseer as geskik vir kommersiële oes, is springbok (Antidorcas marsupialis – Zimmerman, 1780), gemsbok (Oryx gazella – Linnaeus, 1785), koedoe (Tragelaphus strepsiceros – Pallas, 1766), berg sebra (Equus zebra hartmannae – Linnaeus, 1758) en rooihartbees (Alcelaphus buselaphus caama – Pallas, 1766). Eland (Tragelaphus oryx – Pallas, 1766) is ook ʼn geskikte spesies, maar die hoeveelhede wat op een slag geoes kan word, is beperk. Hierdie studie het gedemonstreer dat geslag ʼn invloed op die lewendige gewig van springbok, koedoe en rooihartbees het. Geslag het ook ʼn invloed gehad op karkasgewigte van springbok, gemsbok, koedoe en rooihartbees, maar geen invloed op die karkasgewig van eland nie, terwyl uitslagpersentasie geensins geslagsverskille getoon het vir springbok, gemsbok, koedoe of rooihartbees nie. Nieteenstaande statistiese verskille in die chemiese samestelling van die verskillende spiere van die onderskeie spesies (Mm. biceps femoris, infraspinatus, longissimus dorsi, semimembranosus, semitendinosus en supraspinatus), is dit te betwyfel of verbruikers ʼn onderskeid sal kan tref tussen die spiere. Diskriminant-analise kon nie verskille uitwys tussen die verskillende groepe spiere van springbok en gemsbok nie. Verskille was egter te bespeur tussen verskillende spiere van die rooihartbees. Gedurende hierdie ondersoek is die invloed van seisoen en geslag op die karkasopbrengs en vleiskwaliteit van koedoe en rooihartbees ondersoek. Uitslagpersentasie is beïnvloed deur seisoen, maar nie deur geslag nie. Kleur het betekenisvol verskil tussen seisoene. Resultate van die studie het getoon dat elandbulle meer versadigde vetsure het as koeie, maar dat geen verskille vir geslag gevind is vir poli-onversadigde vetsure nie. Gemsbok-, koedoe - en rooihartbeesvelle het 6 – 7% bygedra tot die lewendige gewig, terwyl die vel van die springbok 4 – 5% bygedra het. Vergelykings van afvalopbrengs tussen spesies het verskille uitgewys ten opsigte van al die items, behalwe die ingewande. Kleinhandelsnitte het betekenisvolle verskille getoon vir die kruis, binneboud, dy en senings. Geen betekenisvolle spesies verskille is opgemerk vir die diklies en bolo nie. Die dy het betekenisvolle verskille tussen geslagte getoon. Geen interaksie tussen spesies en geslag is opgemerk vir die verskillende kleinhandelsnitte van gemsbok en koedoe nie. Mikrobiologiese tellings vir wildsvleis, verkoel vir 6 weke en gevries vir 12 maande, onderskeidelik, het voldoen aan die aanvaarbare vlakke soos voorgeskryf deur die Suid-Afrikaanse kleinhandelsmark. Verskille in fisiese, chemiese en mikrobiologiese kwaliteite was opgemerk vir die salami van die verskillende spesies. Springbok salami was mikrobiologies onstabiel. Die belangrikste karaktereienskappe bemerk tydens die proe van die salami vervaardig van springbok-, gemsbok- , koedoe - en sebravleis, was ʼn oorheersende rook-, sout-, peper- en salamigeur, gekombineer met ʼn rook- en salami aroma. Wildsvleisgeur het nie sterk na vore gekom tydens die sensoriese analise, nie. Die volhoubare gebruik van wild vir kommersiële vleisproduksie het die potensiaal om inkomste vir belangegroepe in die wildsektor te verhoog. Resultate van hierdie studie het kennis uitgebrei wat gebruik kan word om die wildsvleisindustrie in Namibië te ontwikkel.

Thesis (Msc Food Sc (Food Science))--University of Stellenbosch, 2009. / Grape juice is transformed into wine through the complex processes of alcoholic and malolactic fermentation that is performed by yeasts, lactic acid bacteria and acetic acid bacteria. However, the microbes involved in these processes do not only take part in ensuring the successful production of wine, but also cause spoilage of the wine if their growth is not controlled. Conventional, culture-dependent methods of microbiology have been used as the main technique in detecting and identifying these spoilage microbes. Cultureindependent techniques of molecular biology have recently become more popular in detecting possible spoilage microbes present in must and wine, since it allows the detection and identification of viable, but non-culturable microbes and are not as timeconsuming as conventional microbiological methods. The aim of this study was to investigate the sustainability of polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis in detecting wine spoilage microbes inoculated into sterile saline solution (SSS) (0.85% (m/v) NaCl) and sterile white wine and red wine as single microbial species and as part of mixed microbial populations. Three methods of DNA isolation from SSS, sterile white wine and sterile red wine inoculated with reference microbial strains were compared in terms of DNA concentration and purity, as well as simplicity of the technique. These three DNA isolation methods were the TZ-method, the proteinase K-method and the phenol extraction method. DNA could not successfully be isolated from red wine using any of the three DNA isolation methods. The TZ-method was the method of choice for the isolation of DNA from inoculated SSS and sterile white wine as this technique gave the best results in terms of simplicity, DNA concentration and purity. PCR and DGGE conditions were optimised for the universal primer pair, HDA1-GC and HDA2, the wine-bacteria specific primer pair, WBAC1-GC and WBAC2, and the yeast specific primer pair, NL1-GC and LS2. DNA from Acetobacter pasteurianus, Lactobacillus plantarum, Pediococcus pentosaceus, Oenococcus oeni, Brettanomyces bruxellensis and Saccharomyces cerevisiae were amplified with the appropriate primers and successfully resolved with DGGE analysis. PCR and DGGE detection limits were successfully determined when 106 cfu.ml-1 of the reference microbes, A. pasteurianus, Lb. plantarum, Pd. pentosaceus and B. bruxellensis were separately inoculated into SSS and sterile white wine. It was possible to detect low concentrations (101 cfu.ml-1) with PCR for A. pasteurianus, Lb. plantarum, Grape juice is transformed into wine through the complex processes of alcoholic and malolactic fermentation that is performed by yeasts, lactic acid bacteria and acetic acid bacteria. However, the microbes involved in these processes do not only take part in ensuring the successful production of wine, but also cause spoilage of the wine if their growth is not controlled. Conventional, culture-dependent methods of microbiology have been used as the main technique in detecting and identifying these spoilage microbes. Cultureindependent techniques of molecular biology have recently become more popular in detecting possible spoilage microbes present in must and wine, since it allows the detection and identification of viable, but non-culturable microbes and are not as timeconsuming as conventional microbiological methods. The aim of this study was to investigate the sustainability of polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis in detecting wine spoilage microbes inoculated into sterile saline solution (SSS) (0.85% (m/v) NaCl) and sterile white wine and red wine as single microbial species and as part of mixed microbial populations. Three methods of DNA isolation from SSS, sterile white wine and sterile red wine inoculated with reference microbial strains were compared in terms of DNA concentration and purity, as well as simplicity of the technique. These three DNA isolation methods were the TZ-method, the proteinase K-method and the phenol extraction method. DNA could not successfully be isolated from red wine using any of the three DNA isolation methods. The TZ-method was the method of choice for the isolation of DNA from inoculated SSS and sterile white wine as this technique gave the best results in terms of simplicity, DNA concentration and purity. PCR and DGGE conditions were optimised for the universal primer pair, HDA1-GC and HDA2, the wine-bacteria specific primer pair, WBAC1-GC and WBAC2, and the yeast specific primer pair, NL1-GC and LS2. DNA from Acetobacter pasteurianus, Lactobacillus plantarum, Pediococcus pentosaceus, Oenococcus oeni, Brettanomyces bruxellensis and Saccharomyces cerevisiae were amplified with the appropriate primers and successfully resolved with DGGE analysis. PCR and DGGE detection limits were successfully determined when 106 cfu.ml-1 of the reference microbes, A. pasteurianus, Lb. plantarum, Pd. pentosaceus and B. bruxellensis were separately inoculated into SSS and sterile white wine. It was possible to detect low concentrations (101 cfu.ml-1) with PCR for A. pasteurianus, Lb. plantarum, iv Pd. pentosaceus, and B. bruxellensis in SSS when amplified with the HDA1-GC and HDA2 primer pair. A PCR detection limit of 102 cfu.ml-1 was determined in sterile white wine for Pd. pentosaceus and 103 cfu.ml-1 for B. bruxellensis using this primer pair. The results obtained from the PCR amplification with the WBAC1-GC and WBAC2 primer pair compared well with the results of the HDA1-GC and HDA2 primer pair. The results from the DGGE detection limits indicated that it was possible to detect lower concentrations (101 – 102 cfu.ml-1) of A. pasteurianus, Lb. plantarum and Pd. pentosaceus with the HDA1-GC and HDA2 primer pair than the WBAC-GC and WBAC2 primer pair (102 – 104 cfu.ml-1). Lower detection limits were also determined for B. bruxellensis amplified with the HDA1-GC and HDA2 primer pair (103 – 104 cfu.ml-1) than with the NL1-GC and LS2 primer pair (105 cfu.ml-1). PCR and DGGE detection limits for the inoculation of A. pasteurianus, Lb. plantarum and B. bruxellensis at an inoculum of 108 cfu.ml-1 as part of mixed populations in SSS and sterile white wine compared well with the results obtained from the reference microbes inoculated as single microbial species. PCR detection limits of 101 cfu.ml-1 were determined for all three reference microbes inoculated as part of mixed populations when amplified with the HDA1-GC and HDA2 and the WBAC1-GC and WBAC2 primer pairs. It was observed that similar or higher DGGE detection limits were obtained for the reference microbes inoculated in sterile white wine (101 – 107 cfu.ml-1) than when inoculated into SSS (101 – 105 cfu.ml-1). PCR-based DGGE analysis proved to be a technique that could be used successfully with the universal, wine-bacteria and yeast specific primer pairs for the detection of A. pasteurianus, Lb. plantarum, Pd. pentosaceus and B. bruxellensis. The culture-independent technique makes the early detection of possible spoilage microbes at low concentrations in wine possible.

Thesis (M. Sc.Voedselwet.)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Phenolic compounds in wine, due to their antioxidant activity, are reportedly responsible for the health-promoting properties of wines. The effect of cultivar and in-bottle ageing on the antioxidant activity of South African wines in different types of antioxidant assays was, therefore, investigated. The antioxidant activity of commercial South African red (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) and white (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) cultivar wines was compared using the 2,2’-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS·+) scavenging, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH·) scavenging and microsomal lipid peroxidation (MLP) assays. The red wines was more effective than the white wines on an “as-is” and an equal total phenol content. The total antioxidant activity (TAAABTS and TAADPPH) of Ruby Cabernet was the lowest of the red wines, but the antioxidant potency (APABTS and APDPPH) of red wine phenolic fractions did not differ (P ³ 0.05). Ruby Cabernet and Pinotage were the least effective inhibitors of MLP, while Merlot was the most effective of the red wines. Pinotage phenolic fractions had lower (P < 0.05) APMLP than that of other red wines. Of the white wines, Chardonnay and Chenin blanc had the highest and lowest effectivity respectively according to all antioxidant parameters. Ascorbic acid present in some wines increased and decreased their TAA and % MLP inhibition respectively. TAA and % MLP inhibition correlated well (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavanol content of red wines and tartaric acid ester content of white wines. The % MLP inhibition also correlated well with flavanol content of white wines. No correlation (P > 0.01) was obtained between TAA or % MLP inhibition and monomeric anthocyanin content of red wines. In the deoxyribose assay, red wines were more pro-oxidant and exhibited lower hydroxyl radical scavenging and metal chelating abilities than white wines. The effect of in-bottle ageing on antioxidant activity of wines was determined using the ABTS·+ and DPPH· scavenging assays. The TAA and total phenol content of experimental red (Pinotage and Cabernet Sauvignon)and white (Chardonnay and Chenin blanc) cultivar wines, decreased (P < 0.05) during 12 months of storage at 0, 15 and 30 ºC. The TAAABTS of Cabernet Sauvignon and Chardonnay, stored at 30 ºC were lower (P < 0.05) than at 0 ºC. The APABTS and APDPPH of most wines also decreased during storage. The monomeric anthocyanin content of red wines decreased (P < 0.05) rapidly at 15 and 30 ºC. The flavanol content of wines (except Chenin blanc) increased during the first 9 months, decreasing again after 12 months, while minor changes in the flavonol and tartaric acid ester content of both red and white wines were observed. The TAAABTS exhibited a good correlation (r ³ 0.7, P < 0.001) with total phenol content of red and white wines, as well as with flavonol and tartaric acid ester content of red and white wines and flavanol content of white wines. The monomeric anthocyanin content of red wines correlated (r = 0.50, P < 0.001) weakly with TAAABTS. The decrease in the TAAABTS of wines could thus be mainly attributed to a decrease in their total phenol content. / AFRIKAANSE OPSOMMING: Die antioksidant aktiwiteit van fenoliese komponente in wyn is waarskynlik verantwoordelik vir die gesondheidsvoordele daarvan. Die studie het dus gepoog om effek van kultivar en veroudering na bottelering op die antioksidant aktiwiteit van Suid-Afrikaanse wyne te ondersoek. Die antioksidant aktiwiteit van kommersiële Suid-Afrikaanse rooi (Cabernet Sauvignon, Ruby Cabernet, Pinotage, Shiraz, Merlot) en wit (Sauvignon blanc, Chenin blanc, Chardonnay, Colombard) kultivarwyne is vergelyk deur middel van die 2,2’-azino-di-(3-etielbensotialosien-sulfoon suur)-radikaal katioon (ABTS·+) vernietigingstoets, 2,2-difeniel-1-pikrielhidrasielradikaal (DPPH·) vernietigingstoets en mikrosomale lipiedperoksidasietoets (MLP). Die antioksidant aktiwiteit en die antioksidant kragtigheid (AK) van die rooiwyne was beter as dié van witwyne in al drie antioksidant toetse. Die totale antioksidant aktiwiteit (TAAABTS en TAADPPH) van Ruby Cabernet was die laagste van die rooiwyne, terwyl die AKABTS en AKDPPH van rooiwyn fenoliese fraksies nie van mekaar verskil (P ³ 0.05) het nie. Van die rooiwyne, het Ruby Cabernet en Pinotage die laagste en Merlot die hoogste effektiwiteit in die MLP toets getoon. Die AKMLP van Pinotage se fenoliese fraksies was die laagste van die rooiwyne. Die witwyne, Chardonnay en Chenin blanc, het onderskeidelik die beste en swakste antioksidant aktiwiteit en AK van die witwyne getoon in al drie antioksidant toetse. Askorbiensuur wat in sommige witwyne voorgekom het, het die TAA van hierdie wyne verhoog, maar hul % MLP inhibisie verlaag. Die TAA en % MLP inhibisie het goed gekorreleer (r ³ 0.7, P < 0.001) met die totale fenolinhoud van rooi- en witwyne, asook die flavanolinhoud van rooiwyne en die wynsteensuur-esterinhoud van witwyne. Die % MLP inhibisie het ook goed gekorreleer met die flavanolinhoud van witwyne. Geen korrelasie (P > 0.1) is waargeneem tussen antioksidant aktiwiteit van rooiwyne en hul monomeriese antosianien-inhoud. Rooiwyn was meer pro-oksidatief in die deoksieribose toets as witwyne, maar was die swakste hidroksieradikaalvernietigers en metaalcheleerders.Die effek van veroudering na bottelering op die antioksidant aktiwiteit van wyne soos bepaal met die ABTS·+ en DPPH· vernietigingstoetse, is ondersoek. Die TAA en die totale fenolinhoud van eksperimentele rooi- (Pinotage en Cabernet Sauvignon) en witwyne (Chardonnay en Chenin blanc) het afgeneem (P < 0.05) tydens opberging na bottelering by 0, 15 en 30 ºC oor 12 maande. Opberging by 30 ºC het ‘n groter vermindering (P < 0.05) in die TAAABTS waarde vir Cabernet Sauvignon en Chardonnay veroorsaak as by 0 ºC. Die meeste wyne se APABTS en APDPPH waardes het ook verminder (P < 0.05) na 12 maande. Drastiese vermindering (P < 0.05) in die monomeriese antosianieninhoud van rooiwyne is opgemerk tydens opberging by 15 en 30 ºC. Tydens die eerste 9 maande se opberging het die flavanolinhoud van wyne toegeneem (P < 0.05) en daarna afgeneem (P < 0.05) tot by 12 maande, terwyl flavonol- en wynsteensuuresterinhoud van beide rooi- en witwyne min verandering ondergaan het. Die totale fenolinhoud van rooi- en witwyne, asook die flavonol en wynsteensuur-esterinhoud van rooi-en witwyne en die flavanolinhoud van witwyne, het goed gekorreleer (r ³ 0.7, P < 0.001) met die TAAABTS. In teenstelling met die resultate vir kommersiële kultivarwyne, was die TAAABTS van rooiwyne swak gekorreleer (r = 0.5, P < 0.001) met hul monomeriese antosianieninhoud. Die afname in TAAABTS van wyne tydens veroudering kon dus meestal toegeskryf word aan die afname in hul totale fenolinhoud.

Thesis (MScVoedselwet)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Two experiments were conducted in order to manipulate the physical and chemical properties and shelf life of ostrich meat. Experiment 1: The effect of dietary fish oil rich in n-3 fatty acids on the organoleptic, fatty acid and physicochemical characteristics of ostrich meat. The diet of four ostrich groups (15 birds per group), approximately 3 months of age (ca. 41 kg live weight) grazing a predominantly oats pasture, was supplemented with a diet containing 6.7% fish oil. The birds received a supplement of either 0 (diet 1), 800 (diet 2), 1600 (diet 3) or 2400 g (diet 4) DM/day resulting in the consumption of 0 (diet 1), 14.5 (diet 2), 29 (diet 3) and 43.5 (diet 4) g fish oil per day. The ostriches were slaughtered at 10 months of age (ca. 70 kg live weight). An increase in the amount of fish oil consumed was found to have had statistically no significant effect on the sensory characteristics of the M. iliofibularis, although there was a tendency towards an increase in ‘fishiness’, for both aroma and flavour. However, increased concentrations of fish oil had a significant effect on the aroma and flavour of the abdominal fat pads. The muscle pHf and muscle lightness (L*) reflected a significant reduction with increased fish oil levels. The increased feed intake, on the other hand, had no effect on the chemical composition (moisture, protein, fat and ash content) of the meat. The fatty acid profile of both fat and meat was affected by the consumption of fish oil. The SFA concentration increased, while the PUFA concentration decreased, with an increase in feed intake. The MUFA concentration remained constant for all four groups. Experiment 2: The effect of dietary vitamin E and the type of packaging on the sensory quality, physicochemical composition and shelf life of ostrich meat. Two groups of ostriches (35 birds per group; ca. 3 months old) were fed diets containing either 40 mg/kg feed vitamin E (control) or 150 mg/kg feed Vitamin E for nine months. The birds were slaughtered at 12 months of age. The effect of different the levels of vitamin E and heat shrink treatment of vacuum packaging material on the shelf life of refrigerated (0°C) ostrich M. flexor cruris lateralis, was evaluated over 81 days. Vitamin E and heat shrink treatments were found to have had no significant effect on the sensory characteristics; off-meat aroma, sourness, juiciness and mealiness. Rancidity was found to be slightly more pronounced (although not statistical significant) in the vitamin E and heat shrink groups than in the feed control and vacuum-packed groups. A significant decrease in the organoleptic quality of the meat, over a 40 day shelf life period, was observed. The pH and muscle tenderness showed a significant reduction with increased storage time. The purge loss in the package increased over time with no change in muscle drip loss. The colour, conjugated dienoic acid and fatty acid content showed no significant changes over time or with regards to treatment. The total viable counts and coliform numbers in the muscle increased over time, with the coliforms being slightly suppressed by the inclusion of vitamin E in the diet. A microbiological safe shelf life of 40 days at 0°C was obtained. / AFRIKAANSE OPSOMMING: Twee eksperimente is uitgevoer om die fisiese en chemiese eienskappe, asook die rakleeftyd van volstruisvleis, te manipuleer. Eksperiment 1: Die effek van visolie, ryk aan n-3 vetsure, op die organoleptiese, vetsuur- en fisies-chemiese eienskappe van volstruisvleis. Die dieet van vier groepe volstruise (15 voëls per groep), ongeveer 3 maande oud (ca. 41 kg lewende massa) wat ‘n hawer weiding bewei het, is aangevul met ‘n byvoedingsmengsel wat 6.7% visolie bevat en in toenemende hoeveelhede vir die groepe volstruise gevoer is. Die voëls het ‘n aanvulling van 0 (dieet 1), 800 (dieet 2), 1600 (dieet 3) of 2400 g (dieet 4) DM/dag ontvang wat gelei het tot ‘n inname van 0 (dieet 1), 14.5 (dieet 2), 29 (dieet 3) en 43.5 (dieet 4) g visolie per dag. Die volstruise is op ‘n ouderdom van 10 maande geslag (ca. 70 kg lewende massa). ‘n Toename in die hoeveelheid visolie ingeneem, het geen statisties betekenisvolle effek op die sensoriese eienskappe van die M. ilifibularis gehad nie, alhoewel daar ‘n tendens was vir ‘n toename tot ‘n ‘visagtige’ aroma en smaak. ‘n Toename in die konsentrasie visolie het egter ‘n betekenisvolle effek op die ‘visagtige’ aroma en smaak van die abdominale vet neerslae gehad. Die spier pHf en spier ligtheid (L*) het ‘n betekenisvolle afname met toename in voer inname getoon. Die verhoogde olie inname het egter geen effek op die chemiese samestelling (vog-, proteïen-, vet- en asinhoud) van die vleis gehad nie. Die vetsuurprofiel van beide die abdominale vet neerslae en die vleis is deur die inname van visolie verander. Die versadigde vetsuurkonsentrasie het verhoog terwyl die poli-onversadigde vetsuurkonsentrasie verlaag het met ‘n toename in rantsoenvlakke. Die mono-onversadigde vetsuurkonsentrasie het egter konstant gebly vir al vier groepe. Eksperiment 2: Die effek van vitamien E en die tipe verpakking op die sensoriese kwaliteit, fisies-chemiese samestelling en rakleeftyd van volstruisvleis. Twee groepe volstruise (35 voëls per groep, ongeveer 3 maande oud) het voere oor ‘n tydperk van nege maande ontvang wat 40 mg vitamien E/kg voer (kontrole) of 150 mg vitamien E/kg voer bevat het. Die voëls is op 12 maande ouderdom geslag. Die effek van die verskillende vlakke van vitamien E en hitte-behandeling van die verpakkings materiaal op die rakleeftyd van verkoelde (0°C) volstruis M. flexor cruris lateralis, is oor 81 dae geëvalueer. Vitamien E en die hitte-behandeling het geen betekenisvolle effek op die organoleptiese eienskappe (af-vleis aroma, suurheid, sappigheid en melerigheid) gehad nie. Galsterigheid was ‘n bietjie meer gedefinieerd (anie-betekenisvol) in die vitamien E en hitte behandelde groepe as in die rantsoen kontrole en vakuum verpakte vleis. ‘n Betekenisvolle afname is waargeneem in die organoleptiese kwaliteit van die vleis oor ‘n 40 dae rakleeftyd periode. Die pH en taaiheid van die spier het betekenisvol afgeneem met ‘n toename in bergingsperiode. Die drup verlies tydens verpakking het ook oor tyd toegeneem, terwyl geen verandering in die analitiese drup verlies van die spier verkry is nie. Die kleur, gekonjugeerde dieensuur en vetsuursamestelling het geen verandering oor tyd of ten opsigte van behandeling getoon nie. Die Totale Lewendig Seltelling en coliforme het toegeneem oor tyd, terwyl die coliforme deur die byvoeging van vitamien E tot ‘n mate onderdruk is. ‘n Mikrobiologies veilige rakleeftyd van 40 dae is verkry.

Thesis (MSc Food Sc) (Food Science)--University of Stellenbosch, 2005. / Near infrared spectroscopy (NIRS) and UV/Vis spectrophotometric methods were investigated as rapid and/or more economical methods to quantify the major monomeric phenolic compounds, soluble solid content (SSC), total polyphenol content (TPC) and total antioxidant activity (TAA) of green rooibos and Cyclopia genistoides.