Purpose: This study investigated survival and recovery of injured Salmonella spp., Escherichia coli O157:H7, and Listeria monocytogenes on cantaloupe rind surfaces after treatments with water at 22°C, water at 70°C, 3% hydrogen peroxide (H2O2) at 22°C, and a combination of 3% H2O2and water at 70°C for 300 s during storage at 5 and 22°C for seven days.
Methods: Whole melons were inoculated with Salmonella spp., E. coli O157:H7, and L. monocytogenes inocula at 104 CFU/cm2, respectively, and then treated for 300 s with water at 22°C, water at 70°C, 3% hydrogen peroxide (H2O2) at 22°C, or a combination of 3% H2O2 and water at 70°C. Surviving populations including injured bacteria were enumerated on different selective agar plates and the populations inactivated were calculated.
Results: Injured bacteria were among the surviving populations of Salmonella spp., E. coli O157:H7, and L. monocytogenes recovered after treatments with 3% H2O2 alone; 20%, 15%, and 2%, respectively. Populations of injured pathogens on treated cantaloupe lasted for 24 h on rind surfaces stored at 22°C, but declined to <2 CFU/cm2 on melons stored at 5°C. Percent of the surviving populations that were injured when melons were treated with 70°C water, averaged <2% for all pathogens tested. Hot water and a combination treatment with 3% H2O2 at 70°C led to a four log inactivation of all bacterial pathogens. Populations transferred to fresh-cut pieces were below detection, even after enrichment of the samples.
Significance: The results of this study indicated that surviving injured populations of Salmonella spp., E. coli O157:H7, and L. monocytogenes on whole cantaloupes processed for 300 s at 70°C would not pose a microbial safety issue for fresh-cut pieces prepared from treated cantaloupes, when consumed immediately or after storage at 5°C for later consumption.