Bits Contact Us Helpful Hints - Tips for using 3M Petrifilm Sharing ideas for testing a product can benefit everyone. That is why we have this ongoing column containing helpful tips for using 3M Petrifilm plate products. Questions or useful ideas that we directly hear from you inspire many of these tips. When using Petrifilm plates for environmental sampling, be sure to use thiosulfate-free letheen broth if sanitizer may be present.
Letheen broth neutralizes halogen, quaternary ammonium, and acid sanitizers.
Do not use diluents containing thiosulphate or sodium citrate with Petrifilm plates. To ensure accurate results it may be necessary to adjust the pH of acidic foods before plating onto any of the Petrifilm plates for bacterial enumeration. Refer to product literature for specific instructions. The interpretation of blue colonies without gas on Petrifilm E. coli Count plates varies by method. It is important for each food processor to determine the significance of blue colonies without gas for its operation.