Centrifugation and foam fractionation effect on mucilage recovery from Dioscorea (yam) tuber

The yam (Dioscorea spp., Dioscoreaceae) is an important pharmaceutical plant that can be widely applied in the drug industry. The yam tuber is rich in starch and mucilage however, it is difficult to separate the starch from the tuber because of the viscous soluble carbohydrates-protein (glycoprotein) present in the yam. These surface-active complexes produce an extensive amount of foam. Foam fractionation is recognized as a suitable technique for recovering soluble, surface-active substances from a solution using preferential adsorption at the gas-liquid interface. The objective of this research is to compare foam fractionation and centrifugation for recovering the mucilage from yam tuber. The soluble carbohydrates and protein present in the mucilage are analyzed. The results showed that centrifugation may break down the soluble carbohydrates and protein complex, resulting in further soluble carbohydrates and protein separation in different parts of the starch paste and mucilage. With 2 consecutive centrifugations (7300 x g), the total amounts of soluble carbohydrates and protein recovered from the Keelung yam (D. pseudojaponica Y.) tuber were 4.8% and 33.8%, respectively. It was found that excellent soluble carbohydrates (98.8%) and protein (74.1%) yield can be recovered in the Keelung yam using foam fractionation. Foam fractionation provides an alternative method for recovering viscous mucilage from yam. This is especially suitable for starch-rich samples from the tuber