Comparison of molecular structures and functional properties of high-amylose starches from rice transgenic line and commercial maize

High-amylose cereal starches are attracting considerable attention because of their potential health benefits. In this study, the molecular structures and functional properties of high-amylose starches from a rice transgenic line and commercial maize were investigated and compared. High-amylose rice and maize starches had apparent amylose contents of 65.6 and 49.4%, respectively. Compared with high-amylose maize starch, high-amylose rice starch had amylopectin with a higher long branch-chain content and average chain length and with a lower short branch-chain content and degree of branching. High-amylose rice and maize starches exhibited C-type and CA-type crystallinity, respectively. The high-amylose rice starch had a significantly higher gelatinization temperature and lower gelatinization enthalpy, swelling power and pasting viscosity than high-amylose maize starch. High-amylose rice starch had a significantly higher resistance to acid hydrolysis and slightly higher resistance to amylase hydrolysis than high-amylose maize starch. Gelatinized and retrograded starches from high-amylose rice had significantly lower rapidly digestible starch and higher resistant starch contents than high-amylose maize starch. These results were also compared with those obtained from normal rice and maize starches. The significantly different molecular structures of rice and maize starches resulted in their different functional properties.