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M. A. PASCALL, NCFST/FDA, Illinois Institute of Technology, 6502 S. Archer Rd, Summit-Argo, IL 60501 and A. Teo, NCFST/IIT, Illinois Institute of Technology, 6502 S. Archer Rd, Summit-Argo, IL 60501.

The FDA is interested in inspection procedures designed to reduce defective packages that may offer inadequate protection from bacterial contamination of packaged food. Recent increases in the use of polymeric trays with peelable lids, for the packaging of low acid shelf stable foods, has not gone unnoticed. For improved standardization of inspection methodologies for these packages, minimum leak sizes to cause bacterial entry were investigated. This study seeks to determine the minimum leak sizes for entry of Enterobacter aerogenes into post-processed trypticase soy broth packaged in 9oz polymeric trays. After retort processing, channel leaks (in the seals) and pinholes (in the lids) were aseptically inserted into the test packages. These were subsequently immersed into a phosphate saline solution containing a bacterial concentration of 10⁷CFU/mL. The channel leaks were 100, 50, 40, 30, 20, and 10m in diameter and 6mm wide. Pinholes were 50, 40, 30, 20, 15, 10 and 5m in diameter. Only one leak was inserted into each test package. Non-leaking controls were also prepared. All tests were done in triplicate. All packages were immersed in the bacterial solution for 30 minutes at 25^oC then incubated at 35^oC for two weeks. The presence of gas formation was used as an initial indication of E. aerogenes contamination. To confirm this, Gram staining and plating on eosin methylene blue agar was performed. Results indicated that bacterial contamination occurred in packages with channel leaks larger than 20m in diameter by 6mm in length and with pinholes 10m and larger in diameter. Results also showed a positive correlation of leak sizes with bacterial counts in contaminated packages. These results can be used for setting the parameters of on-line leak detection devices for polymeric tray packages, by FDA inspectors during routine food plant inspections, and by regulators during the investigation of recalls and outbreaks.