Sponge versus mini-roller for the surface microbiological control of Listeria monocytogenes, total aerobic mesophiles and Enterobacteriaceae in the meat industry

Abstract

Equipment and surfaces in food industries have a highly variable microbial load and they can be a source of Listeria monocytogenes, which is a pathogen capable of forming biofilms increasing the risk of food contamination. In the present study we have evaluated and compared the efficacy of two environmental sampling procedures, the classical cellulose sponge and a novel procedure, the wool fiber mini-roller. First, two stainless steel surfaces and a polyethylene cutting board were inoculated in the laboratory with four strains of L. monocytogenes isolated from meat products. The recovery percentage of L. monocytogenes varied between 0.17% and 5.83%, and the mini-roller showed higher recoveries than the sponge in the stainless steel surfaces, while the sponge performed better in the polyethylene cutting board. The second part of the study was carried out in 26 meat industries where 69 food contact surfaces were sampled for L. monocytogenes, total aerobic mesophiles and Enterobacteriaceae. Overall, 31.9% sampling points tested positive for L. monocytogenes with the sponge as compared to 26.1% that showed positive with the mini-roller. The mean aerobic counts with the sponge (3.76 log cfu/cm2) were very similar to those obtained with the mini-roller (3.71 log cfu/cm2), and the Enterobacteriaceae counts were somewhat higher with the mini-roller (0.52 log cfu/cm2) than with the sponge (0.07 log cfu/cm2), but the differences were not significant in either case. Results of this study suggest that the novel mini-roller constitutes a sampling procedure which is convenient to apply on surfaces, is cost-effective, and yields equal recoveries of L. monocytogenes, aerobic mesophiles and Enterobacteriaceae than does the classical sponge, and thus could be used for the monitoring of these microbial groups in food contact surfaces.