Effects of Storage and Drying on Cooking Quality of Rice

Abstract

These experiments are conducted to obtain the informations on the effects of storage and drying upon cooking quality of rice. As cooking quality, water-uptake ratio and total solid content in residual cooking water are examined. [table] (1) Effect of storage on cooking quality As aging of rice progresses by storage, water-uptake ratio increases and total solid content decreases gradually. Accordingly, aged rice swells more by cooking and is less sticky in comparison with new rice. The progress of aging is faster when moisture content in rice is more and storage temperature is higher. Moreover, progress of aging depends on variety of rice and is faster in soft-texture varieties than in hard-texture varieties. (2) Effect of heating of rough rice on cooking quality In consepuence of heating in rough rice by high temperature (60°C) for 40 minutes, water-uptake ratio does not change largly but total solid content decreases apparently. Amount of decrease in total solid content depends on moisture content of rice at the start of heating and in general, the higher (especially higher than 18%) the moisture content, the greater the degree of decrease of total solid content. When rough rice is heated by high tempeeature (60°C) for 70 minutes, total solid content is not influenced in low moisture rice, but increases apparently in high moisture rice (18%), because the surface of such rice swells abnormally and disintegrates and partially mixes up in cooking water. Then adequate moist-heat treatment is available to reduce stickiness. (3) Effect of moisture content of rice on cooking quality As moisture content of rice becomes less, total solid content decreases, and decreases notably when moisture content becomes less than 12%. This effect of moisture content on total solid content is more remarkable in soft-texture varieties than in hard-texture varieties, and also has a tendency to be more distinct in rice produced under lower ripening temperature than in rice of same variety produced under higher ripening temperature.