Continuous Aerosol Sampling of Interstitial Headspace for Post-process Contaminants in Dry Foods

Introduction: Detection of post-process biological and chemical contaminants in finished food products are challenging due to the limitations of detecting contaminants that are not typically randomly distributed.  A novel device for aerosol-based sampling of the interstitial headspace of low-moisture foods has been developed which can continuously sample food for contaminants.

Purpose: The goal of this study was to compare the detection of an aerosol-based sampling device to traditional grab sampling for the detection of milk allergen, GloGerm or food surface adhered Enterococcus faecium NRRL B-2354.

Methods: In the first pilot plant study, five grab samples (25 g) each were secured at random from totes of puffed rice cereal (50 lbs), previously spiked in one location with 0.1 g of GloGerm or 0.5 g of dry milk powder. Following sampling, cereal was gravity fed through the device that samples the interstitial headspace (i.e., aerosol) and suspends the contaminant in a 10 ml cartridge containing sterile buffer. In the second pilot plant study 25 lbs of puffed rice cereal were spiked in one location with 30 g of food surface adhered Enterococcus faecium NRRL B-2354 (10⁷ log CFU/g) or 1.0 g of dry milk powder. The inoculated cereal was gravity fed through the sampling device, packaged into 50 g cereal bags and subsequently collected (30 total, every fourth bag).  Enterococcus faecium, milk allergen and GloGerm in the puffed rice cereal and liquid cartridges were analyzed using TSA/KF media, ELISA and fluorescence spectrophotometry. 

Results: This novel sampling device successfully detected the contaminating milk, GloGerm and E. faecium in both studies while the grab sampling approach detected 1 positive out of 15 samples for dry milk powder, and 0 positive in 15 samples for GloGerm. In study 2 the grab samples contained the contaminant in 48.3% and 33.3% of the finished food product for E. faecium and milk allergen, respectively.  The packaging equipment configuration randomized the contaminant distribution more in study 2 relative to study 1.

Significance: This novel aerosol-sampling device has the potential to continuously detect post-process biological and chemical contaminants at a higher incidence relative to traditional grab sampling.