Combined effect of organic acids and supercritical carbon dioxide treatments against nonpathogenic Escherichia coli, Listeria monocytogenes, Salmonella typhimurium and E. coli O157:H7 in fresh pork

Aims: To evaluate the effectiveness of organic acids and supercritical carbon dioxide (SC-CO₂) treatments as well as their combined effect for the reduction of nonpathogenic Escherichia coli and three pathogenic bacteria in fresh pork. Methods and Results: The different treatment conditions were as follows: (i) treatment with acetic (1%, 2% or 3%) or lactic acid (1%, 2% or 3%) only, (ii) treatment with SC-CO₂ at 12 MPa and 35°C for 30 min only and (iii) treatment with 3% acetic or lactic acid followed by treatment with SC-CO₂. Within the same organic acid concentration, the lactic and acetic acid treatments had similar reductions. For the combined treatment of lactic acid and SC-CO₂, micro-organism levels were maximally reduced, ranging from 2·10 to 2·60 log CFU cm ^-2 (E. coli, 2·58 log CFU cm^-2; Listeria monocytogenes, 2·60 log CFU cm^-2; Salmonella typhimurium, 2·33 log CFU cm^-2; E. coli O157:H7, 2·10 log CFU cm^-2). Conclusions: The results of this study indicate that the combined treatments of SC-CO₂ and organic acids were more effective at destroying foodborne pathogens than the treatments of SC-CO₂ or organic acids alone. Significance and Impact of the Study: The combination treatment of SC-CO₂ and organic acids may be useful in the meat industry to help increase microbial safety.