INACTIVATION OF FOOD MICROORGANISMS BY HIGH-PRESSURE CARBON-DIOXIDE TREATMENT WITH OR WITHOUT EXPLOSIVE DECOMPRESSION

In order to elucidate the sterilization mechanism underlying the explo sive decompression system, baker's yeast was pressurized with CO2, N2O , N-2, or Ar gas at 40 atm and 40 degrees C for 4h, and then explosive ly discharged, The survival ratio was markedly decreased only by the t reatments with CO2 and N2O, which are relatively soluble gases in wate r, suggesting that the microorganisms' death may be highly correlated with gas absorption by the cells, Lower decompression rates to atmosph eric pressure, however, led to neither any lower reduction of remainin g cells nor any smaller release of total cellular proteins, Furthermor e, operating with a longer treatment time and smaller number of repeti tions was usually more lethal than with a shorter time and more freque nt repetition, From these results, most of the yeast cells appear to h ave been sterilized during the pressurization process, The spore cells of B, megaterium are considered to have been killed in a somewhat dif ferent manner because of their distinct sensitivity to the applied gas es.