published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

The purpose of this study was to design and develop anti-hyperglycemic functional foods containing phenolic carbohydrate absorption modulator. Physical, chemical, structural and digestive aspects of the reactions of carbohydrates in the presence of phenolic extracts of traditional Chinese medicines were investigated. Water extracts of 14 traditional Chinese medicinal (TCM) plants with reputation of usefulness in treating diabetes were examined for total phenolic contents, antioxidant activities and α-amylase inhibitory activities through in vitro assays. A positive and significant linear relationship between total phenolic content and antioxidant capacity was found (R2=0.99), indicating that the phenolic compounds are the major antioxidant components in the tested materials. Extract of Chinese galls from Rhus chinensis exhibited highest total phenolic content, antioxidant capacity and α-amylase inhibitory activities. The results of this study demonstrate that the extract of Rhus chinensis would be the most effective carbohydrate modulator among the samples tested. Swelling, pasting and thermal properties of wheat and potato starch were studied in the presence of aqueous extract of Galla chinensis (GAC), also known as Chinese galls. The swelling factor was reduced in both starches after GAC extract addition. The extract increased peak viscosity and cold paste viscosity of wheat starch, but decreased those of potato starch. Increased breakdown has shown for wheat starch, but that for potato starch decreased. GAC extract also delayed gelatinization of both starches with higher onset temperature (To). The results of this study demonstrated that GAC extract supplementation can alter the physicochemical properties of wheat and potato starch. To examine the potential application of Galla chinensis (GAC) extract supplementation in Asian white salted noodles, the effects of various GAC extract addition levels on microstructure and in vitro starch digestibility of noodles were investigated. Scanning electron microscopy (SEM) indicated that the gluten protein network was improved (more compact and smooth) by GAC extract in both raw and cooked noodles. The estimated glycemic index (GI) was significantly decreased from 100 to 90.6 after 0.5% GAC extract was added. This indicated that GAC extract supplementation could reduce starch digestibility and blood glucose response. This feature might make GAC extract-enriched noodles sufficiently attractive to health-conscious consumers. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,2008-2009 / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy