Use of continuous bubble separation process for separating and recovering starch and mucilage from yam (Dioscorea pseudojaponica yamamoto)

The yam (Dioscorea pseudojaponica Yamamoto) tuber is abundant in both starch and mucilage. It is difficult to separate yam starch from its tuber because of the presence of viscous polysaccharide polymers (glycoprotein). The surface-active polysaccharide-containing complexes are capable of forming foams. The goal of this study was to develop a continuous bubble separation process for separating and recovering starch and mucilage from yam tubers in the absence of undesirable chemical additives or treatments. The results showed that the highest concentration (13.2 g/100 g) of yam slurry mucilage was obtained with a reasonably high yield of recovered starch (91.2 g/100 g) by treating the starch paste with 1 g/100 g Viscozyme® L and Pectinex® Ultra SP-L. In comparison with the total amount of yam fed into the system, the yield of soluble carbohydrates and protein in separated mucilage were 98.8 g/100 g and 74.1 g/100 g, respectively. The chemical composition of the separated freeze-dried mucilage was shown to be high in soluble carbohydrates (52.5 g/100 g, dry basis) and protein (40.3 g/100 g, dry basis). A very low amount of starch (0.8 g/100 g) remained in the mucilage. This method is simple, low in operational and capital costs, and especially suitable for polysaccharide-protein-containing complexes recovering from a starch-containing system.