Effect of Moderate Heat on the Growth of Bacteria Related to the Fermented Pickles

Abstract

This paper was undertaken to investigate the reason for the immersing of vegetables to hot water for a short time before fermentation in case of manufacturing fermented pickles. When the vegetables were treated with moderate heat at 50°C, Gram negatives were destructed more rapidly than Gram positives. Pseudomonas fluorescens was particularly destructed to 10^-2 after heat treatment at 45°C for 15 minutes. From the leakage of 260nm absorbing substances, orsinol reactive materials and carbohydrates from heated cells of Gram negatives, it was sugested that the damage to the cell membrane and degradation of ribonucleic acid took place within the moderate heat (45°C) treated cells. The viable cells of Gram negatives which were able to reproduce on modified plate count agar medium containing sodium chloride by moderate heat treatment were decreased with increasing concentration of sodium chloride. These results suggested that the salt tolerance of them were lowered by heat treatment. Since Gram negatives containing nitrite producing bacteria contaminating vegetables were easily destructed by moderate heating, nitrite production was depressed at anearly stage of fermentation.