THE IMPACT OF OHMIC HEATING ON RICE GRAIN HARDNESS AND HEATING UNIFORMITY COMPARED TO CONVENTIONAL COOKING METHODS

This study investigated the effects of ohmic heating on rice grain hardness and heating uniformity compared to conventional cooking methods. A self-developed ohmic heating system was utilized to cook rice, and the performance was evaluated against that of a traditional heating. The uniformity of rice temperature and the hardness of rice grains under different water-to-rice ratios were measured using a 5-channel temperature acquisition system and a texture analyzer, and the performance of the two heating methods was comprehensively evaluated. The results indicated that the ohmic heating equipment effectively controlled the temperature variations at each stage, with the maximum heating rate error being 1.24% and the R2 value of the heating curve fitting exceeding 0.9997. Compared to traditional cooking methods, although the temperature difference during the ohmic heating of rice reached 18.32~31.85℃, which is greater than the 21.42~29.94℃ observed in traditional heating, the hardness variation of rice at different locations was significantly lower than that achieved with conventional methods. This was primarily attributed to the fact that as the insulation time was extended, the hardness differences between different layers of rice gradually decreased, ultimately resulting in the hardness of the upper, middle, and lower layers of rice being within the range of 18~21 N, thus achieving a more uniform texture of the rice. The results show that ohmic heating technology has great potential to reduce the rice hardness, and provides theoretical basis and technical support for designing more efficient rice cooking equipment.