Agent for Cooked Rice

It is to provide a method for producing cooked rice with improved loosening properties, anti-aging property, and/or water retentivity, comprising adding and mixing a quality improving agent which is a degradation product of substituted modified starch with a viscosity of 15 mPa·s or higher at 30% by mass in an aqueous solution and 3000 mPa·s or lower at 10% by mass in an aqueous solution, wherein the degradation product of substituted modified starch is obtained by using, as a base material, one or more substituted modified starches selected from the group consisting of hydroxypropyl starch, hydroxypropylated distarch phosphate, and starch sodium octenylsuccinate, and is prepared by subjecting substituted modified starch to hydrolysis treatment with an enzyme in the process of rice cooking for preparing cooked rice.