Improving the microbiological safety of perishable foods is currently a major preoccupation in the food industry. The aim of this study was to investigate the inactivation of three major food pathogens (Listeria monocytogenes [LSD 105-1], Escherichia coli O157:H7 [ATCC 35150], and Salmonella enterica serotype Enteritidis ATCC [13047]) by dynamic high pressure (DHP) in order to evaluate its potential as a new alternative for the cold pasteurization of milk. The effectiveness of DHP treatment against L. monocYtogenes, E. coli O157:H7, and Salmonella Enteritidis was first evaluated in 0.01 M phosphate-buffered saline (PBS) at pH 7.2 as a function of applied pressure (100, 200, and 300 MPa) and of the number of passes (1, 3, and 5) at 25 degrees C. A single pass at 100 MPa produced no significant inactivation of the three pathogens, while increasing the pressure up to 300 MPa or the number of passes to five increased inactivation. From an initial count of 8.3 log CFU/ml, complete inactivation of viable L. monocytogenes was achieved after three successive passes at 300 MPa, while 200-MPa treatments with three and five passes completely eliminated viable Salmonella Enteritidis and E. coli O157:H7, respectively. The effectiveness of DHP for the inactivation of these pathogens was compared to that of hydrostatic high pressure (HHP) using the same pressure (200 MPa, single pass at 25 degrees C). In general, two additional log reductions in viable count were obtained with DHP DHP was less effective against L. monocytogenes and E. coli O157:H7 in raw milk than in PBS. After five passes at 200 MPa, an 8.3-log reduction was obtained for E. coli O157:H7, while a reduction of about 5.8 log CFU/ml was obtained for L. monocytogenes exposed to 300 MPa for five passes. Exposing milk or buffer samples to mild heating (45 to 60 degrees C) prior to dynamic pressurization enhanced the lethal effect of DHP The inactivation of pathogens also depended on the initial bacterial concentration. The highest reduction was obtained when the bacterial load did not exceed 10(5) CFU/ml. In conclusion, DHP was shown to be very effective for the destruction of the tested pathogens. It offers a promising alternative for the cold pasteurization of milk and possibly other liquid foods.

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Six commercial disinfectants were tested for their efficacy in inactivating hepatitis A virus in solution or attached to agri-food surfaces. Disinfectant I contains 10% quaternary ammonium plus 5% glutaraldehyde; disinfectant II contains 12% sodium hypochlorite; disinfectant III contains 2.9% dodecylbenzene sulfonic acid plus 16% phosphoric acid; disinfectant IV contains 10% quaternary ammonium; disinfectant V contains 2% iodide; and disinfectant VI contains 2% stabilized chlorine dioxide. Among these, disinfectants I and II were shown to be the most effective in inactivating hepatitis A virus in solution. The efficacy of these disinfectants was further tested against hepatitis A virus attached to common agri-food surfaces, including polyvinyl chlorine, high-density polyethylene, aluminum, stainless steel, and copper. Disinfectant II was shown to be the most effective, with a maximum inactivation level of about 3 log10. The inactivation efficacy was shown to be affected by the concentration of the active ingredient, the contact time between the disinfectant and the contaminated surfaces, and the incubation temperature. In general, hepatitis A virus was shown to be highly resistant to most disinfectants tested, and high concentrations of active ingredient were needed to achieve acceptable inactivation levels.

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