Gelatinization properties of aged rice and improvement of rice texture by external layer removal

Abstract

Textures of cooked rice prepared from aged rice and improvements in cooked rice through removal of its external layer were investigated. Cooked rice prepared from aged rice became hard and stickiness/hardness (S/H) ratios were significantly lowered in comparison to that of new rice. The cooked rice prepared from aged rice with 7% of the external layer removed became soft and no significant differences existed between the S/H ratios of new rice and aged rice. The soaking solution of rice became starchy solution at the time of heating. The amount of the solid of starchy solution was significantly decreased in aged rice compared with new rice, and that of further polished and aged rice was increased. Therefore, we presumed that the starchy solution became a gelatinous paste layer of starch on the rice grain surface after cooking, and that the amount of the solid of starchy solution was related to the textural deterioration of aged rice and the textural improvement by partial removal of the external layer in aged rice. The RVA pasting properties of the flour in aged rice were also different from those of new rice. However, their changes were different from those for cooked rice texture.