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W. Y. LAM, Dept. of Biology, The Chinese Univ. of Hong Kong, Hong Kong, China and P. C. K. Cheung, Food and Nutritional Sciences Programme, The Chinese Univ. of Hong Kong, Shatin, New Territories, HongKong, China. Mushrooms are used as tonics in traditional Chinese cuisines and considered as valuable sources of non-digestible polysaccharides. Recent studies have solely focused on the physiological effects, for instance, cholesterol-lowering capability, of either the whole mushroom or phytochemicals found in the fungi. However, the physico-chemical characteristics, such as water solubility and viscosity, of the polysaccharide components from mushrooms in relation to their nutritional effects have not been clearly elucidated. Four common jelly mushrooms including Tremella fuciformis, Tremella auricula, Auricularia auricula, and Auricularia polytrica were investigated for their chemical composition. Physical and structural features of the water-soluble polysaccharides extracted from these mushrooms were studied for their potential effects on in vivo hypocholesterolemic activity. Proximate analysis including dietary fiber, protein, lipid, moisture, and ash contents were determined by the AOAC procedures. Mushroom water-soluble polysaccharides were extracted with hot water and purified via dialysis. Total sugar, uronic acids, soluble protein contents, and monosaccharide compositions of the extracts were determined. Total dietary fiber content of T. fuciformis, T. auricula, A. auricula, and A. polytrica was 61, 70, 85, and 59 % dry weight, respectively, in which insoluble fiber was the major component. All mushroom samples contained very low lipid content (0.1 to 1.9% dry weight). Water-soluble extracts of the mushrooms formed viscous solutions with a carbohydrate content between 75 to 79% dry weight and high level of uronic acids (15-18% dry weight). The extracts were particularly rich in xylose and mannose. Since the mushrooms had remarkably high dietary fiber content and contained water-soluble polysaccharides that were highly viscous, they are potential cholesterol lowering agents similar to other high-fiber foods. Experiments are undergoing to investigate the mechanisms of the hypocholesterolemic effect of these mushroom water-soluble polysaccharides in terms of alternations of intestinal absorption of cholesterol, colonic fermentation by-products, and hepatic cholesterol synthesis.
Session 83, Food Chemistry: Antioxidant and bioactive agents
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |