Effect of Lowered and Cycled Storage Temperature of Rice Cooker

Abstract

To improve the quality of boiled rice after storage in rice cookers, temperature was controlled at a lowered condition (45~65 o C repeated temperature cycling), compared to the present commercial rice cookers (75 o C). The effect of lowered temperature cycling on the microbial growth, color of rice, and reducing sugar production was measured. The bacteria Bacillus cereus and B. subtilis were killed at 75 o C and 45~65 o C cycling. The temperature cycling at 45~65 o C prevented an increase in colony forming unit of E. coli more than the steady temperature at 75 o C. Browning during storage was significantly decreased at 45~65 o C cycling, compared to 75 o C. The yellowness increase (Δb value of CIE parameters of the colorimeter) after the 3-day storage was 2.18 at 45~65 o C cycling whereas 9.12 at 75 o C. Reducing sugar was not produced at 75 o C and 45~65 o C cycling but produced at 30 o C because of the microbial growth. In conclusion, the temperature cycling at 45~65 o C can improve the quality of stored boiled rice by decreasing the browning and inhibiting the microbial growth.