FOOD BIOLOGICAL CONTAMINANTS Dry Rehydratable Film Method for Rapid Enumeration of Coliforms in Foods (3M ™ Petrifilm ™ Rapid Coliform Count Plate): Collaborative Study

A rehydratable dry-film plating method for coliforms in foods, the 3MTM PetrifilmTM Rapid Coliform Count plate method, was compared with the U.S. Food and Drug Administration’s Bacterio-logical Analytical Manual method for nondairy foods and the American Public Health Associa-tion’s Standard Methods for the Examination of Dairy Products (SMEDP) method for dairy foods. Six food types, vanilla ice cream, cheddar cheese, fresh refrigerated uncooked pasta, wheat flour, prepared frozen macaroni and cheese, and frozen hash browns, were analyzed for coliforms by 11 collaborating laboratories. For each food prod-uct tested, the collaborators received 8 blind sam-ples consisting of a control sample and 3 levels of inoculated sample, each in duplicate. The mean log counts for the methods were comparable. The re-peatability and reproducibility variances of the Petrifilm Rapid Coliform Count method at 14 and 24 h were not significantly different from those of the standard methods