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.

Abstract

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-method 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 MethodsSM (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 matrixes 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 matrixes evaluated. The range of correlation factor R2 was between 0.9539 and 0.9981, indicating strong correlation between the 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.

Conclusion: The Petricore AC plate is an accurate method for the enumeration of mesophilic aerobic bacteria in the matrixes evaluated.

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