Abstract
The effects of organic acids on the color and texture of cooked white rice mixed with purple-black rice (mixed rice) were examined by using Hinohikari white rice (H-rice) and Murasakinomai purple-black rice (M-rice) polished to 90% and 95%, and unpolished. A 10% (w/w) amount of M-rice was mixed with H-rice and added to distilled water or to a 0.2 M organic acid (acetic, succinic , lactic, malic , or citric acid) in the cooking solution. The L* value was lower in all cooked rice samples with an added organic acid than with distilled water. The a* values of all the mixed rice samples progressively increased with decreasing pH value of the cooking solution, while also progressively increasing with decreasing degree of M-rice polishing in the cooking solution of the same organic acids. The breaking stress of grains in the cooked H-rice and cooked M-rice samples was markedly decreased by adding any organic acid, while the hardness was decreased in all cooked rice samples by adding malic acid or citric acid. The cohesiveness and adhesiveness were markedly increased in all cooked rice samples by adding an organic acid . These results indicate that the color and texture of mixed rice were improved by adding an organic acid to the cooking solution.
