Physicochemical Properties of Starch from High-Quality Hybrid Indica Rice: Insights from National High-Quality Rice Gold Award Chinese Varieties

The physicochemical properties of starch in high-quality hybrid indica rice (HQR) varieties that have received the National High-Quality Rice Gold Award are not well characterized. Ten HQR and two ordinary-quality indica rice (OQR) varieties were selected for this study. All varieties were identically cultivated under late-season conditions in southern China and were subsequently analyzed for differences in taste-related attributes, amylopectin fine structure, and functional properties. Compared with OQR varieties, HQR varieties exhibited a distinct starch profile: lower amylose (16.6–20.2%) but higher amylopectin content (62.6–65.0%), a greater proportion of small and medium starch granules, and a higher ratio of A and B1 chains in amylopectin (with few exceptions). Functionally, HQR varieties showed significantly (p < 0.05) higher gel consistency, solubility, and swelling power, along with higher breakdown but lower setback. They also generally exhibited higher crystallinity and gelatinization enthalpy, alongside a softer texture. Notably, the functional properties showed strong correlations (p < 0.05) with most taste-related attributes and amylopectin fine structures across all varieties. These findings provide critical guidance for future breeding programs aimed at improving the quality of indica rice and developing new elite HQR varieties.