The germicidal efficacy of three common sanitizers (quaternary ammonium compound, iodophor, and chlorine) on Listeria (L. monocytogenes V7, L. monocytogenes Scott A, L. ivanovii, and L. innocua) was studied using the suspension test method at various exposure temperature (2–25°C) and times (0.5–1.5 min). The quaternary ammonium compound, iodophor, and chlorine solutions were prepared with sterile deionized water at concentrations of 25–200 ppm, 12.5–50 ppm, and 25–200 ppm, respectively. All three sanitizers were effective (>5.0-log reduction in CFU/ml in 30 s) against Listeria at 25°C regardless of their concentrations. The quaternary ammonium compound at 100–200 ppm and chlorine at 25–200 ppm inactivated a comparable number of Listeria cells at 2°C as they inactivated at 25°C (i.e., cold temperature did not have any visible effect on the efficacy of the sanitizers). However, the efficacy of the quaternary ammonium compound and of the iodophor at 50 ppm and lower concentrations decreased considerable as the exposure temperature decreased, yet the adverse effect of the cold temperature on the efficacy of the sanitizers was reversed via increasing the exposure time. At cold temperatures, L. monocytogenes V7 and L. innocua were inactivated by the quaternary ammonium compound to a lesser degree than L. monocytogenes Scott A and L. ivanovii.

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