Maryna de Wit

The Effect of Variety and Location on Cactus Pear (Opuntia ficus-indica) Fruit Quality

Little is known about the performance of South African cactus pear varieties in different agro-ecological regions. Effects of locality on internal quality parameters of available cactus pear varieties were examined. With only one exception, no significant differences among the mean replication values for the different parameters between the different locations were observed. The differences between mean values for most individual parameters at the three localities were highly significant. Highly significant differences between the mean values for the measured characteristics were observed, not only among the locations (except for the pulp glucose values), but also for the influences of genotype and interaction between locality and genotype. Significant variations existed between mean values of the different characteristics between localities. Genotype × environmental interactions were noted. It was concluded that Meyers is the most appropriate cultivar for economical purposes in South Africa.

The chemical composition of milk from free-ranging African buffalo (Syncerus caffer)

Milk was obtained from five African buffalo (Syncerus caffer) cows located In the Pilanesberg Nature Reserve and the Phalaborwa district, South Africa. The average nutrient content was 62.9 ± 24.9 g protein, 133.9 ± 80.9 g fat and 51.6 ± 21.0 g lactose per kg milk. The protein fraction respectively consisted of 4.7 ± 3.2 g whey per kg milk and 58.9 ± 21.4 g casein proteins per kg milk. Electrophoresis and subsequent Identification of protein bands showed a migrating sequence of proteins similar to that observed In cattle (Bos taurus) milk. The lipid fraction contained 587.1 ± 50.1 g saturated fatty acids per kg milk fat, and 313.1 ± 35.6 and 27.2 ± 5.8 g/kg mono- and poly-unsaturated fatty acids respectively. Compared to domesticated bovine species, a low content of short and Intermediary chain length fatty acids were observed, while stearic and oleic acid concentrations were higher. Substantial concentrations of uneven carbon chain fatty acids were also observed.

Effect of cultivar, season and locality on lipid content and fatty acid composition of cactus pear seed oil

Opuntia ficus-indica (cactus pear) seeds are rich in linoleic acid and have beneficial properties for nutritional, industrial and pharmaceutical purposes. The total lipid content and fatty acid composition depends on various factors, including cultivar, degree of maturity, climate, harvesting season as well as agricultural practices. The aim of this study was to conduct a comprehensive seed oil quality analysis by investigating variation among cultivars across locations over two seasons. Seed oil content and fatty acid content, as well as the ratios thereof, differed among cultivars, seasons and locations. Cultivar × location × season interactions were significant for oil content. Levels of oleic acid (C18:1c9) were significantly influenced by the cultivar × location interaction. Mono-unsaturated fatty acid content was significantly influenced by cultivar × location and location × season interactions. Oil content was significantly correlated with levels of palmitic acid (C16:0), stearic acid (C18:0) and oleic acid. The cultivars ‘Van As’, ‘Turpin’, ‘Roedtan’ and ‘Meyers’ showed good associations with oil content and C18:1c9, while Bloemfontein was the most stable location.

Acceleration of yoghurt fermentation time by yeast extract and partial characterisation of the active components

Water soluble autolysate of yeast, usually utilised for microbial growth support, was used as additive in yoghurt fermentation. The yeast extract (YE) resulted in a decrease of fermentation time by 21% to reach a pH of 4·6. However, the YE resulted in unacceptable flavour and taste. By size exclusion chromatography, a fraction of the YE was obtained that could account for the observed 21% decrease in fermentation time. The fraction contained molecules of low molecular weight, consisting of minerals, free amino acids and peptides. The acceleration of the yoghurt fermentation was ascribed to the short peptides in the fraction. It is proposed that the application of this extract in industrial yoghurt manufacture would result in savings for both the industry and the consumer.

Cultivar and Harvest Month Influence the Nutrient Content of Opuntia spp. Cactus Pear Cladode Mucilage Extracts

Mucilage extracted from cactus pear cladodes is a hydrocolloid gum. It is a novel, natural, low-kilojoule, cost-effective texture-modifying ingredient in functional food products. Yet, the cultivar with the most optimal nutrient content and the preferred harvest times are as yet unknown. For this reason, mucilage from three Opuntia ficus-indica (Algerian, Morado and Gymno-Carpo) and one Opuntia robusta (Robusta) cultivar were investigated to determine their nutrient content over six months. Nutrients that contribute energy (10.2 kJ/g) were low. The mineral content was high (ash 17.7/100 g), particularly calcium (3.0 g/100 g) and phosphorous (109.5 mg/kg). Low insoluble acid-detergent fibre (1.4 g/kg) and neutral-detergent fibre (2.1 g/kg) values indicated that mucilage was mostly soluble fibre. Calcium oxalate crystals were not detected in dried mucilage. Opuntia robusta powders had higher protein, extractable fat and potassium content, while Opuntia ficus-indica mucilage powders had higher polyunsaturated (Linoleic and α-Linolenic acid) fat content. O. robusta Robusta mucilage, harvested after the fruit harvest (February) had the lowest energy content and the highest mineral and protein content. Mucilage powders were highly soluble, low-kilojoule and mineral-rich. This is a functional ingredient that is produced from an easily cultivated crop, as cactus pears grow in areas with poor soil, extremely high daytime temperatures and limited water supplies.