Public health authorities in Oxford, Middlesex and Elgin Counties, Ontario, seized raw milk Cheddar cheese due to presence of Salmonella muenster. Investigations by these units and the University of Guelph traced the source of Salmonella to one particular milk supplier shipping to a cheese factory. Analysis of milk samples from a herd of 35 cattle revealed only one cow shedding S. muenster directly into the milk (ca. 200 CFU/ml). Eleven of 181 vats of cheese, produced at the factory between May and October 1982, were positive for Salmonella at the curd stage. Only 2 vats of the finished raw milk Cheddar, however, were positive. One lot of Salmonella-positive cheese was still positive after the legally required 60-d holding period and remained so for 125 d.
Effect on the microbiological quality of milk of using a special cleaning detergent (Diversey-Wyandotte, Inc.) for low-temperature (initial 43.8°C, end of wash 35.4°C) washing in a milking parlor pipeline system was compared to regular high-temperature (initial 73°C, end of wash 43.8°C) wash of the system. Microbiological quality of the milk was determined by standard plate count (SPC) and psychrotrophic bacterial count (PBC). Cleanliness of equipment was evaluated by measurement of calcium deposits and visual inspection. Statistical analysis of data over time (June 5 to September 16, 1980) indicated no difference in SPC and PBC of milk between low-and high-temperature washing and, although there was a significant negative slope of PBC with time, this was due to factors other than treatment. Calcium soil deposition and visible evaluation of the equipment were not different for the wash temperatures.
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