Examining the efficacy of mushroom industry biocides on Listeria monocytogenes biofilm

Aims: The aim of this study was to test the efficacy of new and currently used biocides in the mushroom industry for inactivating Listeria monocytogenes biofilm. Methods and results: A laboratory-scale study was initially carried out to test the efficacy of eleven biocidal products against a cocktail of five L. monocytogenes strains that were grown to 3-day biofilms on stainless steel coupons. Biocidal efficacy was then tested under clean and dirty conditions based on the EN 13697:2015 method. The results for the biocides tested ranged between 1·7-log and 6-log reduction of biofilm, with only the efficacy of the sodium hypochlorite-based biocide being significantly reduced in dirty conditions. A pilot-scale trial was then carried out on a subset of biocides against L. monocytogenes on concrete floors in a mushroom growing room and it was found that biocide efficacy in laboratory-scale did not translate well in pilot-scale. Conclusions: Biocides that are used in the mushroom industry and potential alternative biocides were determined to be effective against L. monocytogenes biofilm in both laboratory-scale and pilot-scale experiments. Significance and Impact of the Study: This study has direct impact for the industry as it provides information on the efficacy of currently used biocides and other biocidal products against L. monocytogenes, an added benefit to their primary use.