Purpose: The purpose of this independent evaluation was to compare the new method to the FDA/BAM Chapter 3 method and the SMEDP Chapter 6 method for a broad range of foods as part of the AOAC RI™ PTM validation process.
Methods: A total of 16 matrices were evaluated: raw ground beef, raw ground pork, raw ground turkey, chicken carcass rinsate, fresh swai, fresh tuna, fresh tiger shrimp, easy-peel shrimp, cherry tomato wash, frozen blueberries, Mediterranean apricots, creamy salad dressing, fresh pasta, vanilla ice cream, dry milk powder, and pasteurized skim milk. Naturally contaminated samples for each matrix that covered three target 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. Pasteurized skim milk was evaluated after artificial contamination with a bacterium at 4 levels (uninoculated, low, medium, and high). Each contamination level was evaluated using 5 replicates.
Results: The Mean Log Difference and repeatability were calculated. No significant difference was observed between methods in 13 out of 16 matrices. For fresh tuna and fresh tiger shrimp, a statistically significant difference was observed for the low and high enumeration levels. For raw ground turkey and fresh tiger shrimp, a statistically significant difference was observed for the medium enumeration level.
Significance: This new method demonstrates reliability as a rapid alternative for the enumeration of total viable count in as little as 24 h for a variety of matrices.