Evaluation of Air Samplers for Recovery of Biological Aerosols in Dairy Processing Plants

Abstract

An All Glass Impinger-30 (AGI-30), Andersen 6-stage Sieve Air Sampler (Andersen impactor), Reuter centrifugal air sampler (RCS sampler), and the Millipore open type membrane filter sampler (Filter sampler) were evaluated for viable particle recovery in three dairy processing plant environments. There were two size distribution peaks for viable particles, at stage 1 (>7.0 μm) and stage 3 (3.3-4.7 μm). About 10-12% of the particles were smaller than 2.1 μm in size and were mostly non-molds. During milk processing, the highest number of particles were >7.0 μm in size. But, during ice cream processing and in the idle ice cream room, the highest number of particles were 3.3-4.7 μm in size and were mostly molds. Mean viable particle recovery decreased in the order of AGI-30, Andersen impactor, RCS sampler, and Filter sampler for each of the three sampling environments. These results contrast to those obtained using laboratory-generated aerosols where both the AGI-30 and RCS sampler exhibited low recovery. The increased aerosol recovery by AGI-30 in processing plant compared to laboratory-generated aerosols indicates the presence of carrier and passenger type aerosol particles which disintegrate upon impingement. A comparison of the percent of non-mold cfu recovered by the RCS sampler vs. Andersen impactor indicates that the RCS sampler has a bias toward the detection of non-mold containing particles at all three of the locations tested. The Andersen impactor proved to be the most reliable sampler for recovering biological aerosols from dairy processing plant air.