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.