Green technology for glycemic control: developing rice starch-red rice bran polyphenol complexes through ultrasonication and freeze–thaw treatment

Abstract

Rice bran, an abundant agricultural by-product, offers great potential for zero–waste utilization due to its high polyphenol content. Polyphenols can reduce starch digestibility by forming complexes with starch molecules, and thereby contribute to the development of low–glycemic food products. This study investigated the effects of single or combined ultrasonication and freeze–thaw treatment on complex formation between rice starch and polyphenols extracted from red rice bran. Combined treatment was found to significantly enhance the complexation index, modify functional properties, and alter starch granule morphology. FTIR analysis revealed a peak at 1246 cm−1, indicating the presence of flavonoids, while X–ray diffraction confirmed non–inclusion complexation. The estimated glycemic index decreased from 79.78 (control) to 63.47 under dual treatment with three freeze–thaw cycles. Collectively, these findings demonstrate the potential of green, sustainable processing methods for producing functional, low–glycemic food ingredients while promoting zero–waste utilization of rice bran.