Sake pasteurization using a novel continuous flow pulsed electric reactor with cooling system

A pulsed electric field (PEF) reactor that has two flow paths separated by a membrane was constructed for sake pasteurization. The treatment and cooling solutions were supplied to the flow paths in contact with a ground electrode and a high-voltage electrode, respectively. The characteristics of microbial inactivation in the continuous operation of the novel PEF treatment were investigated using the NaCl solution containing Escherichia coli as the model treatment solution and the NaCl solution as the cooling solution. The effects of the flow rate of the cooling and treatment solutions on the microbial inactivation efficiency and temperature of the treatment solution were investigated. In the PEF treatment at two different treatment solution flow rates, the lower flow rate could achieve effective inactivation, and the temperatures of the treatment solutions after PEF treatment were almost the same. Increasing the cooling solution flow rate was effective in preventing the increase in the temperature of the treatment solution during PEF treatment, but the temperature of the treatment solution remained at around 28 °C when the flow rate was increased. The effects of the electrical conductivity of the cooling solution on the microbial inactivation efficiency and temperature of the treatment solution were also investigated. It was demonstrated that increasing the electrical conductivity of the cooling solution increased not only the inactivation efficiency but also the temperature of the treatment solution after the PEF treatment, and determining the appropriate electrical conductivity of the cooling solution is essential for effective pasteurization. Finally, pasteurization of sake with the reactor using the obtained appropriate electrical conductivity and flow rate of cooling solution was demonstrated. The sake yeast and Lactobacillus homohiochii in sake were fully inactivated by PEF treatment, and the temperature of sake after PEF treatment was maintained below 40 °C. •Cooling through a membrane was effective in controlling the temperature of sake.•The electrical conductivity of the cooling solution affected the inactivation efficiency.•Microorganisms in sake were completely inactivated by PEF treatment.•The temperature of sake after pasteurization by PEF was below 40 °C.