A Survey of Four Fluid Milk Processing Plants for Airborne Contamination Using Various Sampling Methods

Area of Science:

• Food Microbiology
• Environmental Monitoring

Background:

• Air quality is critical in food processing environments to maintain product safety and shelf-life.
• Understanding microbial and non-microbiological particle levels in fluid milk plants is essential for effective contamination control.

Purpose of the Study:

• To assess airborne viable particle counts in commercial fluid milk processing facilities.
• To compare the performance of different air sampling devices.
• To investigate the relationship between viable particles and non-microbiological particles in the air.

Main Methods:

• Air sampling conducted over 4 months in four commercial fluid milk plants.
• Utilized Andersen two-stage, Ross-Microban sieve, and Biotest RCS samplers for viable particles.
• Employed a Met-one laser particle counter for non-microbiological particles.
• Sampling occurred multiple times daily in raw milk storage, processing, and filling areas.

Main Results:

• The Andersen sampler yielded significantly higher viable particle counts (log10 Mean ± SD: 2.03 ± 0.41 to 2.41 ± 0.70 per 100 L) compared to RCS and Ross-Microban samplers (p<0.05).
• Overall correlations between the Andersen sampler and other viable particle samplers were r² = 0.71 (Ross-Microban) and r² = 0.62 (RCS).
• Correlations between Andersen sampler results and total non-microbiological particles (>0.5 μm) were low (r² = 0.15–0.36).

Conclusions:

• The Andersen sampler is a more sensitive method for detecting viable airborne microorganisms in fluid milk plants.
• Non-microbiological particle counts showed a weak correlation with viable particle counts, suggesting different sources or behaviors.
• Results highlight the importance of environmental monitoring and appropriate sampling techniques in ensuring dairy product safety.