Evaluation of Early Staling of Seasoned Cooked Rice Using Squashed Cooked Rice Grains

Abstract

Previously, we presented a novel method for evaluating the early staling of cooked white rice using spectrophotometric and image analyses of squashed cooked rice grains to a certain thickness. Here, we used this new method to evaluate seasoned cooked rice. Concerning the physical properties, salt-seasoned cooked rice was staler than unseasoned rice, and vinegar-seasoned cooked rice was less stale. Seasoning cooked rice with mixed vinegar (a mixture of sugar, salt, and vinegar) caused staling similar to that observed upon vinegar-seasoning, suggesting that even when salt and sugar coexist, vinegar strongly influences the staling of cooked rice. In the measurement of squashed cooked rice grains, Ratio of White Area_α130 , which was calculated from the ratio of the area of gray value 130 or less in a gray-scale image, and L* for salt-seasoned cooked rice were higher after refrigeration for 14 h, and vinegar- and mixed vinegar-seasoned cooked rice exhibited lower values than unseasoned cooked rice. High correlation coefficients were observed between L* and Ratio of White Area_α130 and sensory evaluation results. Thus, we demonstrate that the L* value and Ratio of white Area_α130 of squashed cooked rice grains can indicate early staling of seasoned and unseasoned cooked rice.