87-3 |
The use of magnetic resonance for bacterial contamination detection in packaged shelf stable low acid foods |
M. PASCALL, Dept. of Food Science & Technology, Ohio State Univ., 2015 Fyffe Rd., Columbus, OH 43210, S. Ravishankar, National Center for Food Safety & Technology, Illinois Institute of Technology, IIT Moffett Campus, 6502 S. Archer Rd., Summit-Argo, IL 60501, K. Ghiron, MagTherm, Inc., 860 Broad St., Ste. 100, Emmaus, PA 18049, and J. Johannessen. Many processors of shelf-stable food will store products for a week or more before shipment to ensure the detection of spoiled and contaminated packages using statistical sampling and visual inspection. Such methods cannot prevent occasional defective units from being shipped. Thus, an automated system that can non-destructively test all packages produced would be a major advantage. The objective of this study was to evaluate magnetic resonance (MR) as a non-destructive method for bacterial detection in processed packaged foods. MR relaxation (T2) times were correlated with the growth of B. stearothermophilus and B. subtilis in commercial soymilk packaged in 355mL polymeric trays. These results were compared with viscosity and pH changes in the soymilk caused by these organisms. To perform these tests, 103 CFU of these bacteria were inoculated into individual trays of soymilk, then incubated for up to 28 hours at 55°C and 62 hours at 37°C for B. stearothermophilus and B. subtilis, respectively. Also, MR was studied to determine if it could differentiate between regularly processed cheese sauce and cheese sauce that was modified with µ-amylase as a spoilage simulation. Results showed increased MR T2 sensitivity in the presence of the bacteria after their populations reached 108/mL (after 18 hours) and 107/mL (after 44 hours) for B. stearothermophilus and B. subtilis, respectively. Plate counts showed slower growth of B. subtilis. This organism had an undetectable influence on viscosity but a more profound influence on pH. B. stearothermophilus in comparison, grew faster, lowered the pH, and increased the viscosity of the soymilk. MR was able to distinguish between regularly processed 85g pouches of cheese sauce and other pouches with sauce that were modified with 0.5mL, 1% a-amylase solution. These results showed that MR has the potential to be used for non-destructive identification of contaminated or under-processed foods in polymeric packages.
Session 87, Food Microbiology: General
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