Abstract/Summary

Betalains and beta-carotene extracted from beetroot and carrot wastes, respectively, are natural pigments and offer health benefits. This research primarily focuses on the technological and mechanistic aspects of extracting these bioactives. The extraction of betalains (betacyanin and betaxanthin) is investigated in citric acid and ethanol solutions, whereas the extraction of beta-carotene is studied in sunflower oil. Since the rates of extraction were generally found to be slow due to the use of relatively low temperatures and the possibility of betalains degradation, a mechanistic approach was taken to mathematically model the kinetics of extraction, which was also experimentally validated. This study showed the viability of using elevated temperature short time extraction processes. A modified and generic version of the above model was then developed for the extraction of betalains in aqueous-ethanolic solution, and beta-carotene in sunflower oil and experimentally validated. Finally, the thermal degradation of beta-carotene in sunflower oil was modelled after adopting a schematic reaction network, and experimentally investigated in the temperature range 150-220 °C, in order to explore the possibility of using beta-carotene enriched edible oil for frying, and using the fried product as a vehicle for delivering beta-carotene. The results of this study showed that beta-carotene containing oil can be used as a frying medium to produce fortified potato crisps. Finally, a systematic human trial was undertaken, which demonstrated effective absorption and increased blood plasma concentration of beta-carotene in volunteers who were fed with the fortified potato crisps. In summary, the research presented in this thesis provides considerable new insights into: 1) the mechanisms of extracting betalains and beta-carotenes into solvents, 2) the thermal stability of betalains and beta-carotene in these solvents, and 3) the possibility of using beta-carotene fortified edible oil as a frying medium to produce bioactive fortified fried products which can potentially be used to alleviate vitamin A deficiency.