Inactivation of Escherichia coli O157:H7 by combinations of GRAS chemicals and temperature

Reported outbreaks of food borne illness involving Escherichia coli O157:H7 have increased in the United States during the last decade, with a variety of food products being implicated as vehicles of infection. Studies were carried out to determine the efficacy of combinations of various GRAS chemicals and moderate temperatures to kill E. coli O157:H7. A five-strain mixture of E. coli O157:H7 of approximately 10(8) cfu ml-1 was inoculated into 0(.)1% peptone solutions containing 1(.)0 or 1(.)5% lactic acid plus 0(.)1% hydrogen peroxide, 0(.)1% sodium benzoate or 0(.)005% glycerol monolaurate. The solutions were incubated at 8 degrees C for 0, 15 and 30 min; at 22 degrees C for 0, 10 and 20 min; or at 40 degrees C for 0, 10 and 15 min; populations of E. coli O157:H7 were determined at each sampling time. At 40 degrees C, the pathogen was inactivated to undetectable levels within 10 min of incubation in the presence of 1(.)0 or 1(.)5% lactic acid plus hydrogen peroxide, and within 15 min of incubation in the presence of 1(.)5% lactic acid plus sodium benzoate or glycerol monolaurate. At 22 degrees C, complete inactivation of E. coli O157:H7 was observed after 20 min of exposure to 1(.)5% lactic acid plus 0(.)1% hydrogen peroxide, whereas a reduction of 5 log10 cfu ml-1 was observed with a treatment of 1(.)5% lactic acid plus glycerol monolaurate. None of the treatments resulted in total inactivation of the pathogen at 8 degrees C. The aforementioned treatments could potentially be used to inactivate or reduce E. coli O157:H7 populations on raw produce.