Differences in the functional properties and starch structures of early/late season rice between the early and late seasons

Abstract

In the double rice cropping system, early/late season rice cultivars can be grown in both early and late seasons. However, the functional properties and starch structures of early/late-season rice between the early and late seasons are still unclear. Here, we conducted a field experiment with two typical early/late season rice cultivars. Compared to early rice, late rice had higher hardness and stickiness and lower peak viscosity, breakdown, and pasting temperature. The higher hardness, lower peak viscosity and breakdown of late rice were dominated by its higher amylose content (i.e., the proportion of amylose chains, DP 100–10000). The lower crystallinity and ratio of 1045/1022 cm−1 of late rice was due to its long and very long amylopectin branch chains (DP 25–70), resulting in a lower pasting temperature. We considered that the higher stickiness of late rice was due to a higher proportion of short and medium amylopectin branch chains (DP 6–24). Furthermore, the setback (short-term retrogradation) showed a significant difference between cultivars, which might be related to the difference in long amylopectin branch chains (DP 37–70) and their intermolecular interactions with amylose molecules. These findings are expected to provide important information for improving rice palatability and developing the rice industry of early/late season rice in the double rice cropping system.