Evaluation of 3M Petrifilm Rapid Aerobic Count Plate for Enumeration of Aerobic Microorganisms in Thailand Seafood Products

Introduction: The aerobic plate count (APC) is used to determine the level of microbial burden in foods. When used on seafood products, generally APC does not relate to specific food safety hazards, but it is useful as a quality, shelf life, and post-contamination indicator. Seafood processing plants utilize APC as part of their quality management program to test a large variety of samples including raw materials and finished goods.

Purpose: This study aimed to compare the performance of the 3M Petrifilm Rapid Aerobic Count (RAC) Plate at 32°C and 35°C with the performance of the U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA-BAM) reference method for the enumeration of aerobic organisms in seafood products from Thailand.

Methods: The method comparison was conducted using naturally contaminated seafood matrices (n=55) comprised of (32) fish (17) shrimp and (6) cephalopod samples. Each seafood sample was homogenized and 1 ml of the homogenate was serially diluted in Butterfield's phosphate buffer. Samples (1 ml) were placed onto the RAC Plate and the reference method (FDA-BAM) plates. Colonies were counted after a 24 ± 2-hour incubation at 32 ± 1°C and 35 ± 1°C for RAC plates and a 48 ± 3 hours incubation at 35 ± 1°C for the FDA BAM reference method and the results were compared.  

Results: Coefficients of determination (R²) of 0.9878 and 0.9822 for RAC plates incubated at 32°C and 35°C, respectively, and the reference method indicate a high degree of correlation between both methods.

Significance: 3M RAC plate provided ease of use and addresses the need for faster enumeration of total aerobic microorganisms in seafood products. RAC plates provided results in 24 hours or half the time it takes the for the reference method to produce counts at 48 hours.