The Changes in Structural, Physicochemical, and Digestive Properties of Red Adzuki Bean Starch after Repeated and Continuous Annealing Treatments

Red adzuki bean starch-water suspensions (1:3, w/v) are subjected to repeated and continuous annealing treatments at 55 °C for 96 h. The changes in structural, physicochemical, and digestive properties of starch after both treatments are studied and compared. The results show that the repeated and continuous annealing increases the relative crystallinity of starch without influencing the morphological structure and crystalline patterns. Gelatinization temperatures and enthalpy increase; however starch solubility, swelling power, and viscosity decrease after both annealing treatments. FT-IR analysis shows that annealing treatments result in a reorganization of starch molecules and improve the crystalline perfection. Furthermore, the applied annealing treatments decrease the enzymatic susceptibility of starch and increase the percentage of slowly digestible and resistant starch present. Generally, the repeated annealing results in modified starch with good functionalities compared with continuous annealing. Therefore, repeated annealing can be recommended for producing of modified starch for industrial applications.