Inactivation of Bacillus spores suspended in physiological salt solution, potage and ketchup by the combination of moderate heat and low hydrostatic pressure

The inactivation effect of combined treatment of moderate heat and low hydrostatic pressure (MHP) of B. subtilis, B. coagulans and B. stearothermophilus spores suspended in physiological salt solution and in food materials such as potage and ketchup was investigated. B. coagulans spores were more heat and pressure resistant compared to other spores tested in this experiment. There were 4-8 log cycle reductions of Bacillus spores in potage and physiological salt solution during MHP treatment at 85°C for 12 h, and long time heat treatment could not kill any B. coagulans and B. stearothermophilus spores under the same treatment temperature and time. B. subtilis and B. stearothermophilus spores were completely inactivated at 65°C for 3 h and 85°C for 6 h, respectively, during MHP treatment in physiological salt solution and potage. In ketchup, all Bacillus spores are highly sensitive in both MHP and heat treatments. B. subtilis spores were completely inactivated in ketchup at 75°C and other two strains were inactivated at 85°C. These results indicate that MHP treatment could be utilized in low acid food to achieve high sporicidal activity and used as an effective alternative to high temperature retort processing or ultra high pressurization.