Microwave pretreatment promotes the annealing modification of rice starch

Early indica rice starch can only be modified to a small extent by annealing treatment (ANN), which limits its application. Microwave pretreatment (MW) with different intensity was used to enhance the effectiveness of ANN, and single ANN or MW treatments were used as controls. MW pretreatments per se exhibited insignificant or minor effect on the starch. However, MW pretreatment with appropriate intensity could significantly promote the structural and physicochemical modification of the starch in subsequent ANN, including the enhancement of long- and short-range crystalline structures, the increases in gelatinization enthalpy, particle size, peak viscosity, breakdown and G' value, and the decreases in tan δ value. The MW pretreatment could untangle the entanglements between starch chains by inducing violent movement of the chains, which facilitated the molecular rearrangement and interaction during subsequent ANN, thereby promoting the structural and physicochemical changes. This study provided new insights into the annealing mechanism of starch.