The relationship between the fine structure and physicochemical properties of starches derived from three glutinous rice cultivars

This study examined the regulatory effect of indica–japonica subspecies divergence on the multi-scale structural characteristics and structure–function relationships of glutinous rice starch (GRS) varieties with an ultra-low amylose content. The multi-scale structural features (granule morphology, chain-length distribution, molecular weight, short-range molecular order, crystalline structure, and lamellar architecture) of starches from two indica glutinou rice cultivars (TN and NL) and one japonica cultivar (WK5) were systematically characterized, and their thermal properties and in vitro digestibility were evaluated. All GRS samples exhibited an A-type crystalline structure. TN starch enriched in medium-long amylopectin chains showed the highest relative crystallinity (33.73%), the most compact lamellar structure, superior thermal stability and the highest slowly digestible starch content.NL starch dominated by short amylopectin chains had the loosest lamellar structure, lowest thermal stability and highest rapidly digestible starch content (64.71%). WK5 starch possessed the highest resistant starch content. Correlation analysis revealed that higher molecular weight, longer chains and tighter crystalline structure increased gelatinization temperature, while more branches and longer chains enhanced digestion resistance. These findings provide a theoretical basis for targeted utilization of different glutinous rice cultivars in food processing. • Multi-scale structures of three glutinous rice starches (GRSs) were characterized. • The structure–function relationships of these starches were established. • Indica–japonica divergence modulated the structure–function relationship of GRS. • Amylopectin chain length was a key determinant of GRS functional properties.