The effects of wheat amylose ratios on the structural and physicochemical properties of waxy rice starch using branching enzyme and glucoamylase

Abstract

Based on our previous study, or wheat amylose (WA) can supply an appropriate donor for branching enzyme (BE) to generate more new α-1, 6 branch points in waxy rice starch (WRS), sequential glucoamylase (GA) and BE were used to modify the mixtures of WRS and WA in different amylose ratios. The effects of WA on sequential GA and BE catalysis were investigated and the structural and physicochemical properties of the GABE-modified WRS/WA samples were analysed. The results indicated that after GA→BE treatment, the degree of branching significantly increased with increasing ratios of WRS:WA (1:0.2–1:1.2). With increasing ratios of WRS:WA from 1:0.2 to 1:0.8, short chain length distribution (DP 6–12), solubility and loss tangent increased, whereas middle chain length distribution (DP 13–24), relative crystallinity, the rate of starch retrogradation, the gelatinization temperatures and enthalpy values, as well as storage modulus and loss modulus decreased. However, as the ratios of WRS:WA continued to increase (1:1.0–1:1.2), the above results were reversed. These data demonstrated that amylose ratios in WRS:WA mixtures was closely correlated with catalytic efficiency of sequential GA and BE. The outcome would provide a new pathway for controlling amylose ratios in WRS:WA mixtures to obtain the desirable physicochemical properties of waxy rice starch-based products via enzyme modification.