Performance of non-waxy Japonica rice in the post-cooking storage process and with a varying water-to-rice ratio

Abstract

This study aimed to investigate the effects of the water-to-rice (W/R) ratio and short-term storage after cooking on the physico-chemical properties and starch digestibility of good-eating-quality and conventionally cultivated Yudai 21. Organically cultivated Koshihikari was used as a reference. Polished grains were soaked with water in W/R ratios of ×1.4–×1.7, cooked, and stored at 3°C within 24 h. There was little change in the texture of Koshihikari regardless of the W/R ratio, whereas that of Yudai 21 changed with the W/R ratio, with maximum surface and overall adhesiveness and surface adhesion at ×1.6. The syneresis rate increased with increasing storage duration, and Yudai 21 had a lower syneresis rate (3.4%–3.9%) than Koshihikari (3.7%–4.5%). During storage, surface and overall firmness increased, surface and overall adhesiveness and adhesion decreased, and these changes were greater for Yudai 21 than for Koshihikari. The rapidly and slowly digestible starch, equilibrium concentration of starch hydrolysis, kinetic constant, and estimated glycemic index were not changed by variety and interaction but by storage. This study revealed that Yudai 21 was characterized as a rice with particularly high surface adhesiveness.

Keywords

• Estimated glycemic index
• Kinetics
• Koshihikari
• Tissue structure
• Texture
• Youdai 21