Bactericidal Effect of Freezing with Alcohol

Abstract

Logarithmic growing cells of Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae, Serratia marcescens, Escherichia coli and Micrococcus luteus were killed during a slow freezing to -30℃ with 1% ethanol, or some kinds of monohydric alcohol. The bactericidal effect was proportional to the logarithm of initial concentration of alcohol. The more lethal effect of freezing was observed with such alcohol having a higher straight and saturated arkyl chain less than 4 carbons. Addition of the alcohol soon after freeze-thawing was not lethal to bacteria. Glycerol decreased the bactericidal effect of freezing with alcohol. Concentrated solution of salts and alcohol which formed during freezing might be lethal to bacteria. The freeze-sterilization with alcohol might be applied to frozen foods containing protein or starch.