Survival of foodborne pathogens at different relative humidities and temperatures and the effect of sanitizers on apples with different surface conditions

We investigated the effects of factors such as relative humidity (RH) and temperature on pathogen survival on apples with different surface conditions. Apples with different surface conditions (unblemished, bruised, or cut) were inoculated with three pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, and Staphylococcus aureus) and stored at different RH levels (RH 100, 85, or 68%) at 4 °C or 15 °C for 2 days. S. aureus survived most readily on apple surfaces; it had no significant reduction on any of the apple surfaces for any of the three RH levels after 2 days of storage. The reduction levels of E. coli O157:H7 and S. Typhimurium on unblemished and bruised apple surfaces were higher at RH of 85% and 68% than at RH of 100% at 15 °C; and reduction levels were approximately 3 log₁₀ CFU/apple at 4 °C in RH of 68%. No significant reduction in any of the three pathogens on cut apple surfaces was observed for any RH level. The effectiveness of chemical sanitizers (chlorine sanitizer and 2% lactic acid) in reducing pathogens (E. coli O157:H7, S. Typhimurium, and S. aureus) on apple surfaces (unblemished, bruised, or cut) was also evaluated. Treatment with chlorine sanitizer and 2% lactic acid for 5 min significantly reduced pathogen levels on unblemished and bruised apple surfaces but not on cut apple surfaces. In conclusion, the surface conditions of the apple significantly affected pathogen survival and the effectiveness of sanitizing methods.