Sanitizers have been widely used in controlling cross-contamination during fresh produce washing processes. It is important to identify... Show moreSanitizers have been widely used in controlling cross-contamination during fresh produce washing processes. It is important to identify different approaches for monitoring the efficacy of sanitizer washing. In this study, our objective was to determine the feasibility of indicator microorganisms in assessing the efficacy of chlorine and peroxyacetic acid (PAA) in fresh-cut produce washing. In inactivation experiments, the survivals of inoculated indicator microorganisms [total viable count (TVC), Enterobacteriaceae and total coliforms] and E. coli O157:H7 were determined after exposure to different concentrations of chlorine or PAA in water with added organic load (TOC~200 mg/l). In small-scale washing experiments, bacterial transfer from lettuce leaves inoculated with indicators or E. coli O157:H7 to wash water containing chlorine or PAA with/without organic matters was evaluated. In the inactivation study, higher log reduction was observed for Enterobacteriaceae and total coliforms than for E. coli O157:H7 after chlorine treatment at an initial concentration of 30 ppm. In the bacterial transfer study [a inoculated leaf (~5 log CFU) in 30 ml of wash water], without additional organic matter, approximately 3.5 log total CFU of all bacteria groups was transferred into wash water. Less than 1.5 log total CFU were detected for Enterobacteriaceae, total coliforms and E. coli O157:H7 in 1 ppm chlorine washing. With introduced organic matter, similar microbial loads of Enterobacteriaceae, total coliforms and E. coli O157:H7 were detected on washed leaves and in wash water with initial chlorine concentration of 1 ppm; when initial chlorine level increased to 10 ppm, less than 2 log total CFU of Enterobacteriaceae and total coliforms was detected while about 3 log total CFU of E. coli O157:H7 transferred to wash water, suggesting that chlorine at an initial concentration of 10 ppm could not prevent cross-contamination in the presence of organic load. The indicators showed different levels of survival and transfer from E. coli O157:H7 in this study and were unreliable to effectively monitor the behavior of the pathogen during chlorine wash in fresh produce processes. Enterobacteriaceae and total coliforms were more vulnerable to 40 ppm PAA treatment than E. coli O157:H7 in PAA inactivation experiments. No survival, except for TVC, was observed after 80 ppm of PAA inactivation. In the bacterial transfer study, 40 ppm PAA in wash water was found unable to prevent cross-contamination of indicators and E. coli O157:H7 from leaves to water. Further investigation is needed to compare the bacterial transfer levels of E. coli O157:H7 and the indicators at higher PAA levels. M.S. in Food Safety and Technology, May 2016 Show less
