Studies on the Production of Hydrolyzable Starchy Material in High Concentrated Substrate by Two-Stage Extrusion Cooking Method

Abstract

One of the production methods of hydrolyzable starchy material under high concentration was developed by the addition of thermostable α-amylase using a twin-screw extruder, in order to get more useful application on white rice bran. Paddle screw elements were more effective than kneading screw elements during the first extrusion. On the second extrusion with the addition of thermostable α-amylase, screws assembled by only forward elements were the best one, because temperature increase of the extrudate was small during extrusion. The highly hydrolyzable starchy material manufactured in this series of extrusions was completely gelatinized and over 90% of the α-amylase activity was maintained. The starchy material produced by two-stage extrusion process was hydrolyzable up to 50% based on substrate concentration. Moreover, hydrolyzation by the addition of 0.1% (v/w) glucoamylase could be brought to about 85% of the reducing sugar ratio based on total substrate as sugars after 48hr reaction.