A Starch Molecular Explanation for Effects of Ageing Temperature on Pasting Property, Digestibility, and Texture of Rice Grains.

Alterations in rice qualities during ageing are related to changes in starch molecular structures. However, if and how storage temperature determines starch structure-function relations remain unknown. This study applied four storage temperatures to investigate the effects of ageing on starch structure-function relations. A small but significant variation was observed for starch chain lengths, and this variation depended on both rice varieties and storage temperatures. Rice grains aged at higher temperatures had much higher peak (~25% larger) and setback viscosities (~50% larger) compared to those stored at lower temperatures. The digestion rate constant was lowered (~10%) most significantly at 40 °C. However, the maximum starch digested percentage increased after ageing. All rice varieties showed the lowest hardness at 4 °C and the highest hardness at 40 °C (~20% larger) after ageing. The changes in starch molecular structures were consistent with altered rice properties according to the established structure-property correlations. These results could improve our understanding of the complex rice ageing process.