Evaluation of Selected Sanitizers to Control Bacteria in a Simulated Sweet Water Coolant System ¹

Three types of sanitizers commonly used in dairy processing plants were evaluated at varying concentrations and at 25 and 4°C for their ability to control potential spoilage and pathogenic bacteria in water. Test organisms included Pseudomonas fluorescens , Staphylococcus haemolyticus , and Bacillus spp. These had been isolated from samples of sweet water coolants collected in a previous national survey in grade A dairy plants. S. haemolyticus required 10 ppm chlorine, 12.5 ppm iodine, or 10 ppm quaternary ammonium compound (QAC) to reduce the population >99% at 25°C. At 4°C, however, only 93% of the population of S. haemolyticus was reduced with the 10 ppm QAC. Concentrations of 25 ppm chlorine, 2.5 ppm iodine, or 20 ppm QAC reduced the P. fluorescens population >99% at both 25 and 4°C. The Bacillus spp. was reduced >99% at concentrations of 10 ppm chlorine at 25 and 4°C, 2.5 ppm iodine at 25°C, and 10 ppm QAC at both temperatures. At 4°C, 2.5 ppm iodine reduced the Bacillus population to only 93%. All three organisms were reduced >90% at both test temperatures with concentrations of 25 ppm chlorine, 12.5 ppm iodine, or 20 ppm QAC.