Thesis (M.Sc.)--Chulalongkorn University, 2002

Biological properties of polysaccharide gel (PG) extracted from fruit-hulls of durian (Durio zibethinus L.) were studied to evaluate its resistance to enzyme alpha-amylase activity and lipid entrapment property, in vitro study was performed. Powder of PG swelled and formed a viscous layer in water, 2% PG solution showed 279.36+-25.87 cps. viscosity. PG showed its resistance to alpha-amylase digestion and PG was only partially digested by the enzyme, alpha-helical structure of PG disappeared according to iodine solution test; trace amount of reducing sugar without monosaccharides end product after alpha-amylase digestion was received according to the O-toluidine test compared to maltose standard and TLC technique. PG was also demonstrated resistance against hydrolysis in dilute hydrochloric acid. Lipid entrapment property of PG was investigated in vitro by using semipermeable membrane dialysis technique. Lipids, cholesterol, oleic acid and stearic acid; were determined using PG at 0-2% concentration and bile salt being used as an addition surface active agent to help mixing lipid and water in PG homogeneously. Lipids in solution inside and outside dialysis membrane were analyzed by HPLC technique after 4-16 hours of dialysis. Increasing trapped lipids inside membrane and decreasing released lipids outside membrane were found with respect to increasing PG concentration. 2% PG trapped about 80-90% cholesterol. This result was found comparable to standard polysaccharide glucomannan. PG viscosity was also effected lipids trapping in PG, trapping of lipids in PG increased with respected to increasing viscosity of PG. PG trapping of cholesterol in egg yolk was also studied, the similar result was obtained. In vitro studies of cholesterol releasing from mixture of cholesterol with PG through out the membrane of dissected rat jejunum was performed by using membrane dialysis technique. The similar result was also obtained, increasing concentration of PG resulted in decreasing released cholesterol. The results indicated that PG effect to decrease lipids releasing through rat jejunum wall, according to this study, PG has expected to be use in diet food preparation. In vitro study the effect of dietary fiber on lipid absorption by using semipermeable membrane dialysis may be used in application as a preliminary evaluation of polysaccharide influence lipids absorption