Relationship between the physicochemical properties and amylose content of rice starch in rice varieties with the same genetic background

Abstract

This study analyzed six mutant rice samples from uniform genetic and planting backgrounds with amylose contents ranging from 4.21% to 17.52%. The physicochemical, structural and functional properties of the extracted starches were investigated and their relationships were analyzed. No significant changes were observed in the morphology, granule size, amylopectin chain-length distribution, and crystalline type of rice starches. The average hydrodynamic radius (R_h), relative crystallinity (RC), the ratio of 1045 cm⁻¹/1022 cm⁻¹ (R_1045/1022), and lamellar peak intensity (I_max) were significantly correlated with amylose content, impacting the digestion properties. A higher degree of order in starch structure was found to impede its digestion progress by affecting its physicochemical characteristics. The decreased onset temperature and increased gelatinization temperature range indicated increased crystalline structure instability, decreasing peak time and pasting temperature. Furthermore, there were notable reductions in starch digestion rate (k) and rapidly digestible starch content (RDS) as amylose content increased, despite no significant change in the final digestion percentage. The k exhibited a positive correlation with R_h, while there was a positive association between RC, R_1045/1022, and I_max with RDS. These findings can provide valuable guidance for rice breeders in developing rice varieties with specific functional attributes.