Differences in starch structure, physicochemical properties and texture characteristics in superior and inferior grains of rice varieties with different amylose contents

The difference between superior grains (SG) and inferior grains (IG) is an important factor that directly determines rice yield and quality. In this study, four varieties with different amylose contents were used to examine differences in the starch structure, physicochemical and functional properties as well as texture characteristics between SG and IG. A higher amylose content (AAC), long chain (degree of polymerization ≥ 37) content, average degree of polymerization, and larger granule size were observed in SG, while the short chain (DP 6–12) content and relative crystallinity showed the opposite result. This resulted in a lower swelling factor, higher gelatinization temperature, retrogradation tendency and harder texture in SG. SG were found to have higher slowly digestible starch (SDS) and resistant starch (RS) contents compared with IG, which means a better functional properties. This study indicated that higher amylose and long-chain amylopectin contents in SG probably degrades the rice eating and cooking qualities but improves functional properties as compared with IG.