Effect of freezing, storage and thawing conditions on quality of frozen cooked rice

The effect of freezing and storage conditions on several characteristics of cooked rice balls thawed with microwave-heating were investigated in order to improve the quality of them. Freezing temperature of -13.0 similar to 31.0 degreesC, storage temperature of -31.0 degreesC and storage period within 7days prevented increasing in white cloudiness and yellowness, and maintained the breaking characteristics of the rice balls compared with the values of control samples. In the thawing process with microwave-thawing, no certain tendency was observed between the heating time and the arrival time to the final temperature among the samples. This might be attributed that the rice ball consisted of three-dimensional assembly of rice grain with not same particle shape. The moisture contents in the central part of rice ball was lower than that in the surface part of it after microwave-thawing. As for this, the moisture in the surface part of the rice ball was maintained by wrapping while molecules inside the rice balls were diffused toward surface part by the higher vapour pressure at the center part of the rice balls rising a rapid temperature increase. It was suggested that starch retrogradation not be a predominant role of deterioration of frozen rice, because the degree of gelatinization of starch for rice ball thawed spontaneously showed no certain tendency to the freezing temperature, the storage temperature, and the storage period.