Validation Study of the Petricore™ Aerobic Count (AC) for the Enumeration of Mesophilic Aerobic Bacteria in a Broad Range of Foods and Select Environmental Samples: AOAC Performance Tested MethodSM 032502.

Background: The Petricore™ Aerobic Count (AC) method is used for enumeration of mesophilic bacterial colony counts in a broad range of food and environmental samples. The plate is a ready-to-use dry rehydratable film media composed of modified Standard Methods nutrients, water-soluble-gelling agents and a tetrazolium indicator on the adhesive sheets, and transparent cover film.

Objective: The purpose of this study is to validate the Petricore™ AC for AOAC Performance Tested Methods  SM (PTM) certification.

Methods: Matrix studies were conducted on a broad range of foods and select environmental samples; fresh raw ground beef, fresh raw ground pork, raw bacon, raw shrimp, raw salmon, frozen raw tuna, frozen sliced mushrooms, frozen avocado, frozen blueberries, bacon-lettuce-tomato sandwich, frozen pizza (margherita), cooked sausage (fish and chicken breast), Romaine lettuce, cabbage, fresh green juice, stainless steel surface, plastic surface, and lettuce wash water. Petricore™ AC results were compared to standard method plating procedure results appropriate to each matrix type. Product consistency and stability testing was performed on three production lots of Petricore™ AC, and robustness experiments examined the allowable range of three parameters: culture temperature, incubation time, and inoculum amount.

Results: In the matrix study, equivalent results were observed between the Petricore™ AC method and reference methods for all matrices evaluated. The mean log10 differences between Candidate method and Reference methods were within the ranged from -0.23 to 0.35 log10 within the acceptable range of -0.50 to 0.50 log10. The range of standard deviation values of the candidate method (0.01-0.88 log10) and the reference method (0.02-0.91 log10) were similar in all matrices evaluated. The range of a correlation factor of R2 was between 0.9539 and 0.9981, indicating strong correlation between two methods. In the product consistency/stability study, the Petricore™ AC plate was proven to be equivalent across production lots, and the shelf-life was established at 1 year. Small differences in method parameters did not affect the Petricore™ AC results in robustness testing.

Conclusions: The Petricore™ AC plate is an accurate method for the enumeration of mesophilic aerobic bacteria in the matrices evaluated.

Highlights: The data were reviewed by the AOAC PTM Program and approval was granted for certification of Petricore™ AC as PTM 032502.