Effects of High Pressurization on the Growth ofBacteria derived from Surimi (fish paste)

Abstract

The present study was designed to examine the effects of high pressure on the survival of microorganisms in Surimi (fish paste) and the leakage of materials from bacterial cells treated with high pressurization. The number of survivors in Surimi decreased rapidly after the high pressurization. The most of microorganisms in Surimi was killed by the treatment of high pressure between 300 and 400MPa, and fungi, Gram negatives and Gram positives were sensitive to high pressure in this order. Several pressure-resistant strains were isolated from Surimi and were identified as Moraxella sp. (viable at 200MPa), as Acinetobacter sp. (viable at 300MPa), as Streptococcus faecalis (viable at 400MPa) and as Corynebacterium sp. (viable at 600MPa). It was consequently found that the sensitivities of bacteria in Surimi to high pressurization were different considerably. Examination of the growth curve of each strain treated with high pressurization showed that the starting point of growth curve was retarded more than non-tr ated specimen. Especially the growth of S. faecalis treated with high pressure of 400MPa was retarded abut 20 hours more than non-treated specimen. The release of metal ions from bacterial cells was detected after pressurization. Fe and Mg ions were released particularly. From the leakage of 260nm absorbing substances, orcinol reaction positive materials like RNA and carbohydrates from bacterial cells after treatment of high pressure, it was suggested that the damage of the cell membrane and degradation of ribonucleic acid took place the high pressure treated cells.