Effect of Ohmic Heating Sterilization on the Bacteria Counts in Soymilk

The ohmic heating parameters for sterilizing the soymilk were optimized by response surface methodology(RSM). The effect of temperature,electric voltage and frequency of ohmic heating on the bactericidal rate of the bacteria counts in soymilk was investigated on the base of single factor experiment. Corresponding mathematical model was established by using Box-Behnken design. The results showed that the effect order of three factors was as followed:temperature>voltage>frequency. The optimal specifications of ohmic heating were determined as 82℃,200 V and 190 Hz for temperature,voltage and frequency,respectively. Under the optimized conditions,bacteria sterilization rate could reach to be 100% which was similar to the model predictions. The regression equation was significant,and the mathematical model for the simulation was presented. The number of residual bacterial counts in the soymilk was far less than 1500 CFU/g,meeting the relevant national standards of food safety. The results could provide a theoretical basis for the application of ohmic heating sterilization technology in soymilk processing industry.