Research – Evaluation of sodium hypochlorite and peroxyacetic acid to prevent transfer of surface‐attached Listeria monocytogenes to produce

Wiley Online


Sporadic contamination of produce with Listeria monocytogenes (Lm) is a recurrent problem. Ways for contamination to occur include transfer of the pathogen to produce from processing surfaces or soil particles to which it has become attached. Since it is known that surface‐attached Lm is less susceptible to antimicrobials than Lm grown in liquid culture, the goal of the current study was to determine if Lm grown on surfaces and released into water retained its higher tolerance of antimicrobials. In addition, transfer of Lm from surfaces or soil particles to blueberries, mung beans and spinach leaves in the presence of the antimicrobials, sodium hypochlorite (NaOCl) adjusted to pH 6.8 and peroxyacetic acid (PAA), was studied. The experiments were carried out with a cocktail of six Lm strains and strains obtained from produce processing plants. Results indicated that Lm released from surfaces was as susceptible to the two antimicrobials as Lm grown in liquid culture and was inactivated within seconds by an initial concentration of 100 ppm of NaOCl or PAA. Transfer of Lm grown on stainless steel coupons to blueberries in wash water was not observed at NaOCl concentrations as low as 20 ppm. In contrast, transfer of Lm from washed soil particles (COD = 1.7 ± 0.89 mg/l) in contact with mung beans was observed even at initial NaOCl or PAA concentrations of 250 ppm. Lm released from washed soil particles to which it was attached to spinach leaves could be detected in the presences of 20 ppm of NaOCl and PAA and occasionally even in the presence of 100 and 250 ppm of the antimicrobials.

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