Abstract
Contaminated food-contact surfaces are recognized as the primary reason for recent L. monocytogenes outbreaks in caramel apples and cantaloupes, highlighting the significance of cleaning and sanitizing food-contact surfaces to ensure microbial safety of fresh produce. This study evaluated efficacies of four commonly used chemical sanitizers at practical concentrations against L. monocytogenes biofilms on major food-contact surfaces including stainless steel, low-density polyethylene (LDPE), polyvinyl chloride (PVC), polyester (PET), and rubber. In general, efficacies against L. monocytogenes biofilms were enhanced by increasing concentrations of quaternary ammonium compound (QAC), chlorine, and chlorine dioxide, or extending treating time from 1 to 5 min. The 5-min treatments of 400 ppm QAC, 5.0 ppm chlorine dioxide, and 200 ppm chlorine reduced 3.0–3.7, 2.4–2.7, and 2.6–3.8 log10 CFU/coupon L. monocytogenes biofilms depending on surfaces. Peroxyacetic acid (PAA) at 160 and 200 ppm showed similar antimicrobial efficacies against biofilms either at 1- or 5-min contact. The 5-min treatment of 200 ppm PAA caused 4.0–4.5 log10 CFU/coupon reduction of L. monocytogenes biofilms on tested surfaces. Surface material had more impact on the efficacies of QAC and chlorine, less influence on those of PAA and chlorine dioxide, while organic matter soiling impaired sanitizer efficacies against L. monocytogenes biofilms independent of food-contact surfaces. Data from this study provide practical guidance for effective disinfection of food-contact surfaces in food processing/packing facilities.
Highlights
As a critical foodborne pathogen, Listeria monocytogenes causes approximately 1,600 cases of infection and 260 cases of death annually in the United States (Scallan et al, 2011)
Increasing the quaternary ammonium compound (QAC) concentration from 200 to 400 ppm improved its efficacy against L. monocytogenes biofilms on different food-contact surfaces except low-density polyethylene (LDPE) surface for both 1- and 5-min exposures (Figure 1)
The concentrations of QAC, chlorine dioxide, chlorine and Peroxyacetic acid (PAA) against L. monocytogenes biofilms on common food-contact surfaces were selected complying with FDA regulation (FDA, 2017)
Summary
As a critical foodborne pathogen, Listeria monocytogenes causes approximately 1,600 cases of infection and 260 cases of death annually in the United States (Scallan et al, 2011) It has been implicated in multi-state outbreaks on fresh produce including cantaloupes (CDC, 2012), prepackaged caramel apples (CDC, 2015a), bean sprouts (CDC, 2015b), frozen vegetables (CDC, 2016a), and packaged salads (CDC, 2016b) since 2011. L. monocytogenes form biofilms on SS, PVC, LDPE, PET, and rubber surfaces (Krysinski et al, 1992; Beresford et al, 2001; Takahashi et al, 2010; Doijad et al, 2015; Papaioannou et al, 2018), exerting enhanced resistances to acid and sanitizer treatments (Ibusquiza et al, 2011; van der Veen and Abee, 2011), which makes routine disinfection in a food processing facility more difficult
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