Inativação de escherichia coli O157:H7 e bacillus subtilis por água ozonizada

Abstract

The objective of this work was to evaluate the efficacy of ozonized water on the inactivation of Escherichia coli O157:H7 and Bacillus subtilis. The sanitizer was evaluated at concentrations of 0.6, 0.8 and 1.0 mg.L-1 applying contact time of 1, 3 and 5 minutes. The ozone efficacy was evaluated through the enumeration of microorganisms before and after processing. E. coli O157:H7 decimal reductions varied from 1.9 to 6.6 after 1 minute of contact time at concentrations of 0.6, 0.8 and 1.0 respectively. At other exposure time evaluated (3 and 5 minutes) a total E. coli O157:H7 inactivation (> 8 decimal reductions) was reached. For Bacillus subtilis, after the first minute of contact, at a concentration of 108 spores mL-1, decimal reductions varied from 2.5 to 5.3 at concentrations of 0.6 e 1.0 mg.L-1 respectively. After 3 minutes of contact time spores were inactivated within 5.8 log cycles at a 1.0 mg.L-1 concentration. The results showed that the main ozone activity occurs up to one minute of contact, however, it have an residual activity up to 5 minutes, which allows the application of lower ozone concentration (0.6 mg.L-1) to reach safe levels of microbial inactivation combined to longer periods of exposure. The ozonized water has proved to be an effective sanitizer for the inactivation of Escherichia coli O157:H7 and Bacillus subtilis