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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.

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Starch is isolated from kernel of acorn fruit (Quercus fabri) using different methods, including hot‐water soaking (HWS), alkaline washing (ALW), ultrasonic‐assisted ethanol soaking (UAES), and ultrasonic‐assisted hot‐water soaking (UAWS). Structural and physicochemical properties of starches isolated using these methods are investigated. The surface structure of acorn starch granules varies depending on the isolation method. However, a similar C‐type crystalline pattern is found for all the isolated starch samples. Acorn starches isolated using the ALW and UAES methods exhibit a greater degrees of crystallinity than those of starches isolated using the other methods. FT‐IR spectra analysis reveals that the chemical bonds in starch molecules are not affected during the isolation of acorn starch under different conditions. Moreover, starch isolated using the UAES method exhibits the greatest water solubility, swelling power, and light transmittance values, as well as the lowest tannin content. In addition, the lightest white color is found for starch isolated using the ALW method. Furthermore, the HWS and ALW methods result in acorn starch with greater enthalpy and gelatinization temperatures, whereas the UAES and UAWS isolation methods result in acorn starch with greater peak viscosity. The obtained results provide important knowledge about the differences in physicochemical properties of acorn starch isolated using different methods.