Masters Degrees (Food Science)

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Browsing Masters Degrees (Food Science) by Author "Ampem, Gilbert"

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    Quality attributes of pomegranate fruit and co-products relevant to processing and nutrition
    (Stellenbosch : Stellenbosch University, 2017-03) Ampem, Gilbert; Opara, Umezuruike Linus; Fawole, Olaniyi Amos; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH SUMMARY: Pomegranate fruit, owing to its health benefits, has served several important applications in industrial processing and nutrition. However, knowledge of the physico-chemical and textural properties of the fruit relevant to processing and nutrition remains critical. Presently, the South African pomegranate industry has great concerns on key issues governing pomegranate fruit processing. These issues are centered on understanding how pomegranate fruit properties influence prospect for value addition, processing and nutrition; what extent do cultivar differences influence the ease of processing and suitability as a raw material in food processing; and how to classify pomegranates based on their potential as source of raw materials for health-promoting compounds. Based on these, the overall aim of the study was to add value to commercially cultivated pomegranate (‘Wonderful’, ‘Acco’ and ‘Herskovitz’) in South Africa by evaluating their physical, textural and chemical properties, including the nutritional and mineral compositions, and quality attributes and functional properties of the kernels and oil constituents of these cultivars with emphasis on processing. Investigation of the physical properties of ‘Wonderful’, ‘Acco’ and ‘Herskovitz’ showed no significant differences in whole fruit weight, length, diameter, geometric mean diameter, surface area and volume of oblate spheroid among the cultivars. However, Wonderful and Herskovitz fruit cultivars had the highest (61.62%) and lowest (56.98%) edible portion, respectively. In addition, the arils of ‘Acco’ yielded the highest juice volume (74.05 mL/100 g arils i.e. 74.05%). Furthermore, juice extracted from ‘Wonderful’ contained the highest total soluble solids (15.93°Brix) while ‘Herskovitz’ fruit juice was characterised by high titratable acidity (1.32% citric acid). The textural properties in terms of maximum forces to cut, puncture and compress the fruit, distinguished ‘Wonderful’ whole fruit from the other cultivars. These textural tests characterised Wonderful cultivar as the hardest and therefore would require higher mechanical energy than the other cultivars during processing. The physical and textural properties of fresh and dried arils and kernels relevant to processing and nutrition were also investigated. As expected, the loss of moisture in fresh arils and kernels resulted in a significant reduction in weight and lineal dimensions. However, kernel index, shape index as well as compressibility characteristics of both arils and kernels increased for the cultivars after drying. From value-addition viewpoint, the kernels of Acco cultivar contained the highest oil yield (27.39%), proteins (18.73%), energy (1655.60 kJ/100 g), moisture (0.24%), ash (3.55%) and dietary minerals. On the other hand, kernels of ‘Wonderful’ and ‘Herskovitz’ were rich in carbohydrate (30.65%) and dietary fibre (36.48%), respectively. In addition, dietary mineral profiling of pomegranate kernel was in the order of Nitrogen (2453.00 – 3047.00 mg/100g) > Potassium (846.67 – 1646.00 mg/100g) > Phosphorus (380.33 – 500.67 mg/100g) > Magnesium (144.33 – 204.67 mg/100g) > Calcium (138.33 – 152.67 mg/100g) > Sodium (10.67 – 21.55 mg/100g) > Iron (5.28 – 5.72 mg/100g) > Zinc (2.91 – 3.94 mg/100g) > Copper (1.89 – 2.58 mg/100g) > Manganese (1.40 – 1.99 mg/100g) > Boron (0.96 – 1.82 mg/100g). These amounts are within the Recommended Daily Allowance (RDA) proposed by European Union and United States of America. These findings may therefore help processors and nutritionists to improve food formulations with pomegranate kernels. The study was further extended with special interest on pomegranate kernel oil (PKO). The yield of PKO ranged between 16.59 – 27.39% and were in the order ‘Acco’ > ‘Herskovitz’ > ‘Wonderful’, regardless of extraction solvent. Acetone extracted PKO with light yellow colour and also, with high amounts of phenolics, tocol, α- and γ-linolenic acids and para-anisidine value. However, among the cultivars, PKO of ‘Herskovitz’ had the highest para-anisidine value suggesting its weak resistance to oxidation. Punicic acid, a unique conjugated linolenic acid in PKO, ranged between 59.90 – 69.85% and were in the order of petroleum ether > n-hexane > acetone. In addition, the investigated PKO exhibited high (89.50 – 91.60%) radical scavenging activity, regardless of cultivar and extraction solvent. In terms of oil stability, storage temperature and duration affected properties of PKO. In comparison with oil stored at 25ºC, a remarkable reduction in punicic acid and increase in α- and γ-linolenic acids were observed in PKO stored at 60°C. This study showed that PKO of ‘Wonderful’, ‘Acco’ and ‘Herskovitz’ could potentially serve as good source of bioactive oil. Overall, this study presents scientific background on how pomegranate cultivars could influence the ease of processing, and their suitability as sources of raw materials for health-promoting compounds in nutraceutical industries.