Hydroxypropylation and acetylation of rice starch: effects of starch protein content.

This study investigated the impact of starch proteins on the hydroxypropylation and acetylation of rice starch. Hydroxypropylated (HP) and acetylated (AC) starches were synthesized using rice starch prepared by protease digestion with and without purification. The protein content of purified starch (CONP) was not changed by derivatization, but that of crude starch without purification (COPR) decreased. The reactivity was slightly lower in HP-COPR but were identical between AC-starches. The relative crystallinity was higher for HP-COPR and AC-COPR. HP-COPR and AC-COPR showed lower swelling power and solubility than HP-CONP and AC-CONP, respectively. Higher gelatinization enthalpies were observed in modified starches from COPR. Pasting viscosities were similar between HP-starches and were higher in AC-CONP than in AC-COPR. Overall, COPR is a potential source of chemically modified starches with a reduced production cost; however, it should be noted that the starch protein content affects the reactivity and physical functionality of modified starches. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01106-y. © The Korean Society of Food Science and Technology 2022.