Characterization of yam (Dioscorea opposita Thunb.) mucilage and polysaccharide with different varieties

Abstract

The mucilage in yam tuber is very important factor for the viscosity of yam. But there are a number of unclarified points regarding mucilage of yam, the present report therefore aims at presenting basic data on the mucilage from three kinds of yam (Tsukuneimo, Ichoimo, Nagaimo). The results obtained were as follows : Viscosity of tororo and mucous solution from yam indicated high rate in the order, Tsukuneimo, Ichoimo, Nagaimo. The mucilage were composed mainly sugar and protein, and most of sugar composition was mannose. The main amino acids in the mucilage were isoleucine, leucine and glycine. Isolated mannan from the mucilage had molecular weight about 18 000 on gel filtration. The I.R. spectrum, periodate oxidation and methylation analysis of the mannan indicated that they were β (1→4) linked mannan, which had a small degree of branching at the C-3 position of the mannose residue, one out of 17 units for Tsukuneimo, 14 units for Ichoimo, 9 units for Nagaimo. It was found that as high units of chain length as high viscosity and was identical with turn obtained in viscosity.