Pre-soaking treatment can improve cooking quality of high-amylose rice while maintaining its low digestibility

Abstract

Rice is a staple food for more than half of the world's population and it is regarded as a high glycemic index (GI) food. Breeders developed high amylose rice having low digestibility, but it also has inferior palatability. This study used high-amylose rice (HAR) produced by gamma irradiation and compared the digestion and physicochemical properties related to palatability with those of low-amylose rice (LAR). Pre-soaking and different-pH treatments were adopted to find a way to enhance the palatability of HAR while maintaining its low digestibility. After pre-soaking, HAR had a higher water uptake ratio (4.68 vs. 4.11 g g⁻¹), proportion of leached starch (16.6 vs. 12.6%) and adhesiveness (77 vs. 39), but lower setback (0.092 vs. 0.107 Pa s), hardness (10.1 vs. 12.6 kg) and resilience (0.20 vs. 0.25). The results showed that pre-soaking was able to enhance the quality of the cooked rice mainly by modifying the starch amorphous region while maintaining the low digestibility of HAR. Pre-soaking can be adopted as a practical and effective household cooking method to prepare rice with relatively low digestibility and good palatability.