Effects of high-pressure carbon dioxide on Escherichia coli in nutrient broth and milk

Bactericidal effects of high-pressure carbon dioxide against Escherichia co li were studied under 100, 75, 50 and 25 bar at 20 degreesC, 30 degreesC an d 40 degreesC. E. coli suspended in nutrient broth (NB, pH = 6.75) was inac tivated under 100, 75. 50, and 25 bar CO2 treatments for 50, 65, 100, and 1 40 min at 30 degreesC, respectively. Acidification of nutrient broth by dis solved CO2 alone might account for the bactericidal effect under pressure. E. coli was inactivated in NB with initial pH 5.50 and 4.5 at 100 bar for 8 0 and 95 min, respectively. Treatment at 100 bar CO2 pressure for 6 h cause d a decrease of 6.42 and 7.24 log cycles in whole and skim milk, respective ly. (C) 2001 Elsevier Science B.V. All rights reserved.