The effect of heating conditions on the physical and chemical properties of “zengayu” were studied by analytical methods and sensory tests. Rice gruel cooked at a low heating rate had lower water absorption and swelling, and was harder during the initial period of heating. While rice gruel cooked at high heating rate had higher water absorption and swelling, and quickly became softer during the initial period of heating, it did not soften homogeneously throughout the whole rice grain with prolonged heating time. In contrast rice gruel cooked at a medium heating rate had the greatest adhesiveness throughout the heating period, and rice gruel cooked at the low heating rate had a larger quantity of reducing sugar. Sensory tests indicated that all the rice gruel samples heated for 50 min had a similar taste from all the heating conditions and such rice gruel was preferred most.