Combination effect of saturated or superheated steam and lactic acid on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes on cantaloupe surfaces

The purpose of this study was to evaluate the effectiveness of the combination treatment of lactic acid immersion and saturated or superheated steam (SHS) on inactivation of foodborne pathogens on cantaloupes. Saturated steam (SS) treatments were performed at 100 degrees C, while SHS treatments were delivered at either 150 or 200 degrees C. Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes-inoculated cantaloupes were exposed to 2% lactic acid or sterile distilled water for 1 min followed by a maximum of 20 s of SS or SHS. Populations of each of the three pathogens on cantaloupes were reduced to under the detection limit (1.0 log CFU/cm(2)) after the combination treatment of 2% lactic acid and 200 degrees C steam for 20 s. To compare the effect of the lactic acid treatment method, we conducted spray application with 2% lactic acid combined with SS or SHS treatment; however, no significant log reduction differences were found between immersion and spraying techniques. After combination treatment of cantaloupes for 20 s, color and maximum load values (a characteristic of texture) were not significantly different from those of untreated controls. The results of this study suggest that the combination treatment of lactic acid and SHS can be used as an antimicrobial intervention for cantaloupes without inducing quality deterioration.