Purpose: The purpose of this independent evaluation was to compare the new method to the ISO 21527:2008 parts 1 and 2 and the FDA BAM Chapter 18 method for a broad range of foods as part of the AOAC Research Institute™ validation process.
Methods: A total of 10 matrices were evaluated: yogurt, sour cream, almonds, sliced apples, frozen bread dough, ready-made pie, sandwiches, dehydrated soup, fermented salami and frozen ground beef patties. Naturally contaminated samples that covered three levels of contamination (low level 10 -100 CFU/g, medium level 100-1,000 CFU/g, and a high level 1,000-10,000 CFU/g) were analyzed. Those not naturally contaminated were artificially contaminated with a yeast or mold, and 5 replicates were analyzed at 4 levels (uninoculated, low, medium, and high).
Results: A paired t-test was conducted at P = 0.95 for each matrix. No significant difference was observed between methods in 4 out of 10 matrices (yogurt, apples, ground beef and sausage.) For 5 of the matrices, sour cream, sandwiches, ready-made pie, almonds, and frozen bread dough, a statistically significant difference was observed for the high level of detection with the new method. No significant statistical difference was observed among the new method and both of the reference methods for the low and medium levels for each of the five matrices. For dehydrated soup, the new method recovered 3 separate levels of the target organism, but no recovery of the target analyte was detected by the reference methods.
Significance: The new Rapid Yeast and Mold Count Plate Method demonstrates reliability as a rapid alternative for the enumeration of yeast and mold in as little as 48 hours.