Forty responses were obtained from a questionnaire sent to regulatory agencies of market milk and manufactured dairy products of the 50 state governments. Replies indicated that air-borne contamination was considered most important in the commercial processing or manufacture of cultured milks followed by dry milks, cheese, market milks, ice cream, and butter in decreasing order of importance. However, a high percentage of replies signified a lack of knowledge of airborne contamination in processing or manufacture of dairy products.
Air was sampled using the Casella sampler to ascertain the standard plate count and yeast and mold count in critical product areas of various size dairy plants in nine states. The following results were obtained/ft3: (a) cheese: SPC, >115.7 mean and 3 to >702 range, yeast and mold, 29.1 mean and 1 to 99 range; (b) dry dairy products: SPC, 31 mean and 8 to 60 range, yeast and mold, 28.9 mean and 3 to 84 range; (c) market milk: SPC, 31.3 mean and 4 to 89 range, yeast and mold, 30.8 mean and 0 to 132 range; (d) butter: SPC, 45.2 mean and 11 to 132 range, yeast and mold, 12.3 mean and 4 to 26 range; and (e) ice cream: SPC, 16.4 mean and 10 to 25 range, yeast and mold, 8.4 mean and 4 to 16 range.
The most obvious increase in bacteria counts seemed to be caused by an increase in number of people passing close to the sampling probe and a greater amount of dust from unpaved roads adjacent to the plant.
1Paper presented at the 55th Annual Meeting of the international Association of Milk, Food, and Environmental Sanitarians, St. Louis, Missouri, August 18–22, 1968.
2Michigan Agricultural Experiment Station Journal Article No. 4523.