Sampling of Microbial Aerosols at Various Locations in Fluid Milk and Ice Cream Plants

Potential sources of aerosol contamination and dairy products' containers in four commercial dairy plants (fluid milk and ice cream) were sampled for microorganism-containing particles and residual bacterial count (RBC), respectively, over a 3- month period. Microbiological analyses included total aerobes (TA), staphylococci (ST), and yeasts and molds (YM). The Biotest RCS sampler was used for air sampling. All aerosol sources sampled in this study indicated significant increase in the microbial content of the air when compared to air in plants without processing activity. However, when comparisons are made between exit air from the ventilation system (filtered air) and other aerosols sampled during processing activity, only the drains, water spraying, and personnel activity were associated with significant increases in TA and ST. Half and/or whole gallon retail containers were sampled 2 to 3 times per d in four plants. The RBC of containers from each of the four plants did not exceed one CFU per ml of capacity.