Masters Degrees (Consumer Science)
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Browsing Masters Degrees (Consumer Science) by Author "Osthoff, G."
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Item Open Access Antioxidant content and potential of fresh and processed cladodes and fruit from different coloured cactus pear (Opuntia ficus-indica and Opuntia robusta) cultivars(University of the Free State, 2013-02) Du Toit, Alba; De Wit, M.; Osthoff, G.English: Different coloured cactus fruit, peel, seeds and cladodes were studied for antioxidant content and -capacity in fresh products. Fruit and cladodes from seven different cultivars from the O.ficus-indica spp. and one of O. robusta spp. were collected representing the four colours of fruit available namely, green, pink, orange and purple. It was found that fresh cactus pear fruit and cladodes contained exceptionally high levels of Ascorbic acid, Total Phenolics and Betalains and modest amounts of Carotene. Antioxidant potential remained at very high levels regardless of the specific antioxidant content. The highest antioxidant content and -capacity were found in purple (O.robusta Robusta) fruit and cladodes, attributed to the high levels of Betalains. Ascorbic acid, working synergistically with Phenolics, was found to provide almost as much antioxidant capacity to orange fruit coloured cultivars. It was thus found that cultivars with purple and orange fruit and cladodes were the best in regards to antioxidant content as well as -potential. Five cultivars, representing the four colours were further investigated by processing into different products in order to determine the influence that preservation techniques had on the antioxidant content and potential in the fruit, peel and cladodes. Juice, dried products, chutneys, whole preserves and pickles were prepared from the fruit (pulp), peel and cladodes of the five different coloured cultivars that attained the highest values in the fresh study. Betalains were retained in processed products; Ascorbic acid was mostly preserved in the processed products that involved minimal heat treatments, while Carotene and Phenolics increased after processing. Processed cladodes, more than fresh cladodes, from all the cultivars, were concluded to provide an excellent source of antioxidants and could be suggested for products such as cladode flour and pickles. The peel in general was found to contain very similar antioxidant content and potential as the fruit and should be included in products when possible. In fruit, the purple fruit is highly recommended for processing, as it displayed the highest antioxidant potential in its fresh form and maintained these levels in processed product. Dried fruit is the product with the highest source of antioxidants to the consumer. Juice and chutney from pink or orange fruit would also provide products that the South African consumer is accustomed to with exceptionally high antioxidant potential. The study brings to light the potential that cactus pear products have for the food industry. It could be developed into a profitable industry if the public could be made aware of the health benefits that they provide.Item Open Access Nutritional composition, descriptive sensory analysis and consumer acceptability of products developed from Agave americana flowers(University of the Free State, 2014-02) Semuli, Makamohelo; Bothma, C.; Osthoff, G.English: The nutritional composition of agave flowers was determined and the following nutrients were analysed: moisture (86.62%); energy (226 kJ/100 g); proteins (1.71 g/100 g); fat (0.46 g/100 g); dietary fibre (2.12 g/100 g); K (207.77 mg/100 g); Mg (53.06 mg/100 g); Ca (48.33 mg/100 g); P (32.12 mg/100 g); Na (1.27 mg/100 g); Fe (1.03 mg/100 g); Zn (0.66 mg/100 g); Cu (0.04 mg/100 g); and Mn (0.15 mg/100 g). In contrast to many vegetables, the flower samples contained sugars in the form of sucrose (0.52 g/100 g), glucose (0.77 g/100 g), fructose (1.06 g/100 g) and maltose (0.69 g/100 g). The vitamin C content was 1.03 mg /100 g, but no vitamin A was detected. When compared to other flower vegetables, the agave flower had the lowest contents for protein, P, K, Mn, Na, Cu and vitamin C, but the highest value for fat. The agave flower and artichoke had similar values for energy, moisture and Mg, while the cauliflower and agave compared well in regard to Ca and Zn contents. Broccoli had similar contents for protein, fibre, P and Cu. The agave had higher values for energy, and fat than cauliflower, and higher fat and Ca, Fe, Mg, P and Zn values than broccoli. Artichokes had lower contents for moisture, fat, Ca and Zn than the agave flowers. Broccoli and cauliflower were moister than the agaves. Descriptive sensory analysis was used to investigate how various treatments would influence the sensory properties of Agave americana flowers. Blanched and unblanched flowers, subjected to three treatment methods (steaming, stir frying and pickling), were analyzed by ten trained panelists, in three replications. The data was analyzed using principle component analysis. A lexicon of 20 attributes was generated, including 11 for the steamed treatment, an additional six for the stir fried treatment and another four for the pickled treatment. Of these, three descriptors were for the attribute aroma, six for mouthfeel, five for appearance, four for taste and one for aftertaste. The unblanched pickled agave flowers were characterized by crunchy, fibrous and chewy mouthfeel, bitter taste, green pepper colour and cactus appearance, and a cucumber odour. For the blanched pickled agave flowers, taste descriptors were prominent, namely sweet, sour and sweet-sour, followed by a sweet aftertaste, combined with a moist appearance. For all the unblanched flowers, regardless of treatment, some of the descriptors had negative connections, like fibrous, bitter, cactus and rancid. Descriptors for the blanched flowers, again regardless of treatment, were more favourable and included sweet, sour and sweet-sour taste, and green bean and nutty odour. Three panels of 50 members each participated in the consumer acceptance tests, one each for the steamed breads and chocolate cakes, and one for the stew and deep fried flowers. Apart from acceptability, aroma, taste and texture were also evaluated for the baked products. The breads, cakes and stews were defrosted at 4 ºC overnight. The breads and cakes were left at room temperature (22ºC) before serving, while the stews were served heated. The breads, fritters and stews were prepared with blanched flowers, while the cake was made with unblanched flour. All the products were acceptable, but in different degrees. The scores were lower for aroma and final acceptability of the bread, due to unfamiliar texture experienced by the consumer panel. The agave cake scored lower for aroma and taste, but higher than the bread on texture. The stews and battered agave fritters were liked by the consumer panels and scored between 6.92 and 7.26 on the hedonic scale.