Harvesting Time Modulates Starch Structure, Physicochemical Properties and In Vitro Digestibility of Wuyoudao4...

Harvesting time is an important but insufficiently characterized factor affecting rice starch structure and digestibility. Wuyoudao4 (WYD4) rice was harvested weekly from 45 to 87 days after heading to investigate changes in starch structure, physicochemical properties, and in vitro digestion. With delayed harvesting, starch crystallinity of cooked rice decreased from 6.27% to 4.97%, while total amylase and α-amylase activities increased significantly. Rice flour particle size (D10 and D90) was reduced after mid-harvest, indicating improved enzyme accessibility. Consequently, starch digestibility at 120 min increased from 80.53% (week 1) to 95.60% (week 7). Kinetic analysis confirmed a single-stage digestion mechanism, with enzyme binding as the rate-limiting step and higher digestion extent at later harvest time. These results demonstrate that harvest time modulates rice starch digestibility through coordinated changes in crystallinity, enzymatic activity, and particle accessibility, providing new mechanistic insight into harvest-dependent starch digestion behavior.