Chewing characteristics of rice and reasons for differences between three rice types with different amylose contents

Abstract

This study investigated the physicochemical structural changes in different types of rice (japonica rice [JR], indica rice [IR], and waxy rice [WR]) during oral digestion and explored the reasons for differences in oral digestion between the three different types. The results showed that, compared with JR (42.41 ± 3.06 mg/g) and WR (26.82 ± 0.67 mg/g), IR had the highest amylose content (49.95 ± 3.33 mg/g) and, related to this, hydrolysis rate. A correlation analysis showed that, the higher the amylose content, the harder the texture of rice, leading to longer chewing times and, as a result, a greater degree of hydrolysis. In addition, the higher the amylose content, the lower the exudate content and viscosity of rice, which affects chewing time and frequency, thereby affecting the degree of hydrolysis. Both X-ray computed tomography and scanning electron microscopy indicated that cooked IR had the loosest structure and the most pores, that were conducive to chewing and crushing and therefore contributed to the high hydrolysis rate. Analysis of the exudate structure showed that the amount of exudate affected rice pores. More exudates lead to pore coverage and a tight structure.