Resistant starch content and physicochemical properties of non-waxy rice starches modified by pullulanase, heat-moisture treatment, and citric acid

Physicochemical modification methods have been widely applied to increase resistant starch (RS) content of waxy starch, but their effects on the functional properties of non-waxy starches are not fully understood. In this study, five non-waxy rice starches with intermediate to very high apparent amylose contents (AAC) were modified by pullulanase (PUL), heat-moisture treatment (HMT) and citric acid (CA). RS contents, AAC, crystalline structures, pasting properties and thermal properties were analyzed. The three modification treatments were effective in increasing the RS contents, especially CA modification. PUL modified starches had relatively higher AAC and relative crystallinity (RC), and their crystalline patterns changed from A-type to mixed B + V type. Both HMT and CA increased gelatinization temperature significantly but had opposite effects on changing paste viscosity of different rice starches. Compared with other non-waxy rice varieties, high-amylose rice starch exhibited the highest RS, AAC, and RC after modification. This study provides practical information for improving the nutritional benefits of rice.