Inactivation of Lactobacillus fructivorans in physiological saline and unpasteurised sake using CO2 microbubbles at ambient temperature and low pressure

Summary The ability of carbon dioxide microbubbles (MB‐CO2) to inactivate Lactobacillus fructivorans suspended in physiological saline and unpasteurised sake at ambient temperature and a pressure lower than 2.0 MPa was investigated. The number of L. fructivorans cells in physiological saline solution containing 15% ethanol showed a 6‐log reduction following MB‐CO2 treatment at 40 °C and 2.0 MPa for 50 min. The effectiveness of the treatment increased concomitantly with temperature, pressure and ethanol concentration of the sample solution but was unaffected by the glucose concentration in the sample solution. Furthermore, the number of L. fructivorans cells showed a 5‐log reduction in sake after MB‐CO2 treatment at 40°C and 2.0 MPa for 60 min. Sensory evaluation revealed no significant difference between MB‐CO2‐treated sake and unpasteurised sake. These results indicated that MB‐CO2 treatment was highly effective for the inactivation of L. fructivorans and might become a practical method for pasteurising sake at ambient temperature.