Multi-scale structural heterogeneity of glutinous rice starch in different varieties: A determinant of physicochemical properties and digestibility.

This study systematically investigated the multi-scale structure of glutinous rice starches (WK1, WK2, WK3, TN2072, and HY) from five varieties, and analyzed physicochemical properties and in vitro digestibility to reveal structure-property relationships. TN2072 starch exhibited distinctive structural characteristics showing a lower gyration radius (245.77 nm) and crystalline lamellar thickness (5.7249 nm), demonstrating a more compact molecular structure than those of the other starches. The proportion of short chains of amylopectin (DP 6-12, 23.09-42.16 %) was negatively correlated with both ΔH (7.91-11.23 J/g) and gelatinization temperature (70.15-80.70 °C), while showed positive correlation with peak viscosity (2185-2866 cP). Structural parameters of starch such as high double helix content, high relative crystallinity, and low lamellar thickness were associated with lower enzymatic hydrolysis rates in starch and a high content of resistant starch. Meanwhile, a high proportion of medium and long chains (DP ≥ 13) was conducive to the formation of ordered, compact crystal and lamellar structures, which was the key determinant for high gelatinization temperature and low digestibility. These findings revealed that the multi-scale structure of glutinous rice starch varied with different varieties, and determined the physicochemical properties and digestibility, providing a theoretical foundation for variety selection for specific industrial applications.