Starch Molecular Structure: The Basis for an Improved Understanding of Cooked Rice Texture

Much is known about factors affecting rice texture, but the underlying molecular reasons for the observations are less well understood. Cooked rice displays multiple textural attributes, of which the major ones are hardness and stickiness. A unified molecular mechanistic description of the cause of these two textural attributes is summarized. Amylose molecules may entangle and/or co-crystallize with amylopectin chains in the crystalline lamellae, thereby causing limited starch swelling during rice cooking and a harder texture. An increase of the amount of amylopectin, the proportion of short amylopectin chains, and amylopectin molecular size in the leachate during cooking, create a greater opportunity for bonding and molecular interaction, causing more force to be needed to make the grains come apart, i.e. a higher stickiness. This improved understanding of rice texture will help rice breeders, rice industry and consumers to manage and improve the cooking and eating quality of cooked white rice.