Effectiveness of activated persulfate in removal of foodborne pathogens from romaine lettuce

Abstract

Activated persulfate could be an alternative sanitizer for fresh produce decontamination. This study is the first in reporting the potential of activated persulfate in reducing Escherichia coli O157:H7 and Listeria monocytogenes from romaine lettuce surface. Ferrous sulfate and sodium hydroxide were used as the activators. Both activation methods achieved up to 3.5 log CFU/g reductions of E. coli O157:H7 and L. monocytogenes on romaine lettuce in 5min. Higher persulfate level and longer treatment time lead to higher pathogen reductions. The wash water after each treatment was also collected and analyzed. E. coli O157:H7 survived in the wash water for both activation methods except when persulfate concentration reached 70 mmol/L. L. monocytogenes survived under all treatment conditions except for alkaline activation with persulfate concentration at 700 mmol/L. This might be due to the higher resistance of L. monocytogenes against activated persulfate treatment. Furthermore, both activation methods showed decreased efficacy in pathogen removal at refrigerated temperature. However, they achieved equal or higher reduction efficacies than electrolyzed oxidizing water (100 mg/L), bleach (100 mg/L), and peroxyacetic acid (78 mg/L) at both 20 and 4 °C. In addition, under current test conditions no significant color deterioration was found on activated persulfate treated lettuce.