Peroxyacetic acid and chlorine dioxide unlike chlorine induce viable but non-culturable (VBNC) stage of Listeria monocytogenes and Escherichia coli O157:H7 in wash water

Pilar Truchado,Maria I Gil,Ana Allende

doi:10.1016/j.fm.2021.103866

Pilar Truchado, Maria I Gil + Show 1 more

Open Access

https://doi.org/10.1016/j.fm.2021.103866

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Abstract

The elaboration of guidelines for the industry to establish minimum concentration to prevent cross-contamination during washing practices based on operational limits is the core of the recommended criteria for the use of sanitizers. Several studies have evidenced that sanitizers reduced the levels of foodborne pathogens. However, they might lead to the progress into a viable but non-culturable (VBNC) state of the cells. This evidence has raised concerns regarding the effectiveness of the recommended washing practices for the inactivation of microbial cells present in the process wash water (PWW). The present study evaluated if the most commonly used sanitizers, including sodium hypochlorite (chlorine), peroxyacetic acid (PAA) and chlorine dioxide (ClO2) at established operational limits induced the VBNC stage of Listeria monocytogenes and Escherichia coli O157:H7. Prevention of cross-contamination was examined in four different types of PWW from washing shredded lettuce and cabbage, diced onions, and baby spinach under simulated commercial conditions of high organic matter and 1 min contact time. The results obtained for chlorine showed that recommended operational limits (20–25 mg/L free chlorine) were effective in inactivating L. monocytogenes and E. coli O157:H7 in the different PWWs. However, the operational limits established for PAA (80 mg/L) and ClO2 (3 mg/L) reduced the levels of culturable pathogenic bacteria but induced the VBNC state of the remaining cells. Consequently, the operational limits for chlorine are satisfactory to inactivate foodborne pathogens present in PWW and prevent cross-contamination but higher concentrations or longer contact times should be needed for PAA and ClO2 to reduce the likelihood of the induction of VBNC bacteria cells, as it represents a hazard.

Highlights

Washing is a critical process in the commercial operation of fresh-cut produce, as it is a major source of cross-contamination between different product batches (FDA, 2008)
Commercial sanitizers are needed to maintain the microbial quality of the process wash water (PWW) and prevent cross-contamination of the product (Gil et a., 2009; Gombas et al, 2017; Maffei et al, 2017)
The differences observed can be due to the inflow of microorganisms inside the washing tank and to the physiological state of the bacteria present in the PWW apart from the organic input increasing chlorine demand in wash water (Weng et al, 2016)

Summary

Introduction

Washing is a critical process in the commercial operation of fresh-cut produce, as it is a major source of cross-contamination between different product batches (FDA, 2008). Commercial sanitizers are needed to maintain the microbial quality of the process wash water (PWW) and prevent cross-contamination of the product (Gil et a., 2009; Gombas et al, 2017; Maffei et al, 2017). The residual concentrations of these sanitizers in the washing tank to maintain the microbial quality of the wash water have been recommended or limited by scientific studies, guidelines and regulations. For chlorine is 20 mg/L (Tudela et al, 2019), 80 mg/L for PAA (21CFR173.315) and 3 mg/L for ClO2 (FDA, 2019) These are general recommendations as a case-by-case study should be performed to determine the operational limits under commercial washing practices. The differences observed can be due to the inflow of microorganisms inside the washing tank and to the physiological state of the bacteria present in the PWW apart from the organic input increasing chlorine demand in wash water (Weng et al, 2016)

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