Comparative characterisation of structural, physicochemical and digestive properties of rice starches isolated from novel high‐amylose mutants

Summary Novel high‐amylose rice mutants with unique starch properties were developed from a low‐amylose rice variety. The objective of this study was to explore the impacts of apparent amylose content and amylopectin structure on the physical and nutritional properties of rice starch by comparing novel mutants with conventional rice varieties. The rice mutants demonstrated a specific amylopectin characteristic, indicating an extremely lower portion of short chains (15.2%–16.5%) than the other rice varieties (27.3%–31.1%). The starch gel prepared from the rice mutant exhibited significantly higher compressive and breaking stress than the other high‐amylose rice variety with a higher apparent amylose content, indicating that amylopectin characteristics markedly influenced the starch gel structure. The rice mutant demonstrated the highest content of undigested starch after 120 min of digestion in raw starch (50.5%) and starch gel (53.0%). The starch from newly developed rice mutants were found to have markedly high resistance to digestion due to its amylopectin structure and formation of harder gel.