Comparison of Petrifilm™ and Plate Count Methods for Enumerating Molds and Yeasts in Cheese and Yogurt.

The Petrifilm™ method for enumerating yeasts and molds was evaluated on 52 samples of fresh cheese and yogurt. A conventional plate method on glucose yeast extract medium with oxytetracycline was used as reference. Counting the repeatability a value of 0.229 log units was obtained for the Petrifilm™, compared to 0.175 for the conventional plate method. The correlation coefficient was 0.9978 with a residual standard deviation of 0.094 log units. The Petrifilm™ method is practical and fast, and its results may be compared to those of the conventional plate method.