4. AOACRIMicroMethods-2018Awards

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664 B ird et al .: J ournal of AOAC I nternational V ol . 99, N o . 3, 2016 FOOD BIOLOGICAL CONTAMINANTS

Evaluation of the 3M™ Petrifilm™ Rapid Aerobic Count Plate for the Enumeration of Aerobic Bacteria: Collaborative Study, First Action 2015.13 P atrick B ird , J onathan F lannery , E rin C rowley , J ames A gin , and D avid G oins Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214 R obert J echorek 3M Food Safety Department, 3M Center, Bldg 260-6B-01, St. Paul, MN 55144 Collaborators: K. Angeles, K. Beers, B. Brahmanda, A. Brandt, R. Brooks, B. Brown, N. Cuthbert, C. Fagundes, K. Gonzales, A. Hankins, L. Hardrath, B. Kupski, C. Lopez, J. Marchant-Tambone, A. Mastalerz, W. McMahon, J. Meyer, K. Miller, A. Morris, K. Payne-McDaniel, J. Pickett, J. Reynolds, R. Rodgers, J. Schoeni, L. Thompson, H. Wright

A erobic plate counts are often used in the food industry to gauge the sanitary quality of food commodities throughout the production process, starting from raw materials used as ingredients to the shelf-life stability of finished products (1). Although generally not used as a safety indicator in food products, aerobic plate count can be useful in providing information on the deficiencies in sanitation systems or flaws in process control systems (2).This test can alsobe useful inproviding information on the sanitary conditions of storage and processing facilities (1). Cultural enumeration of aerobic microflora can take 48–72 h, depending on the matrix, and can produce wide-ranging results as a result of difficulties that arise in the discernment of bacterial counts from matrix particulate. The 3M™ Petrifilm™ Rapid Aerobic Count (RAC) Plate uses a cold-water-soluble gelling agent and dual-sensing indicator technology to facilitate the enumeration of aerobic bacteria after 24 h of incubation for most foods (48 h for dairy powders, including whey powders). The 3M Petrifilm RAC Plate allows for the simple and rapid enumerationof aerobic bacteria in the food andbeverage industries. Samples are diluted in Butterfield’s phosphate diluent (BPD) and a sample aliquot is plated onto the 3M Petrifilm RAC Plate. The sample aliquot is dispersed throughout the growth area and the plates can be incubated at either 32 or 35°C, depending on the matrix. Enumeration of colonies can occur in as little as 24 h of incubation for most matrixes. Enumeration is made easier due to the indicators in the gelling agent that use color to distinguish bacterial colonies from food particles. Prior to the collaborative study, the 3M Petrifilm RAC Plate was validated according to AOAC validation guidelines (3) in a harmonized AOAC Performance Tested Method SM (PTM) study. The objective of the PTM study was to demonstrate that the 3M Petrifilm RAC Plate accurately enumerated aerobic bacteria in select foods as claimed by the manufacturer and that no difference in repeatability was observed between the 3M Petrifilm RAC Plate method and the reference methods. For the 3M Petrifilm RAC Plate PTM evaluation, 16 matrixes were evaluated: raw ground beef, raw ground pork, raw ground turkey, chicken carcass rinsate, fresh swai, fresh tuna, fresh tiger shrimp, raw easy-peel shrimp, cherry tomato wash, frozen blueberries, dried Mediterranean apricots, creamy salad dressing, fresh pasta, vanilla ice cream, instant nonfat dry milk (NFDM), and pasteurized skim milk.

The 3M™ Petrifilm™ Rapid Aerobic Count (RAC) Plate is a sample-ready culture medium system containing dual-sensor indicator technology for the rapid quantification of aerobic bacteria in food products. The 3M Petrifilm RAC Plate was compared to the U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA BAM) Chapter 3 (Aerobic Plate Count) for the enumeration of aerobic bacteria in raw easy-peel shrimp and the Standard Methods for the Examination of Dairy Products (SMEDP) Chapter 6 (Standard Plate Count Method) for the enumeration of aerobic bacteria in pasteurized skim milk and instant nonfat dry milk (instant NFDM). The 3M Petrifilm RAC Plate was evaluated using a paired study design in a multilaboratory collaborative study following current AOAC validation guidelines. Three target contamination levels (low, 10–100 CFU/g; medium, 100–1000 CFU/g; and high 1000–10 000 CFU/g) were evaluated for naturally occurring aerobic microflora for each matrix. For raw easy-peel shrimp, duplicate 3M Petrifilm RAC Plates were enumerated after 24 ± 2 h incubation at both 32 and 35°C. Pasteurized skim milk 3M Petrifilm RAC Plates were enumerated after 24 ± 2 h incubation at 32°C, and instant NFDM 3M Petrifilm RAC Plates were enumerated after 48 ± 3 h incubation at 32°C. No statistical difference was observed between 3M Petrifilm RAC Plate and FDA BAM or SMEDP reference methods for each contamination level. Submitted for publication January 6, 2016. Corresponding author’s email: pbird@qlaboratories.com This method was approved by the Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces as First Action. The Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces invites method users to provide feedback on the First Action methods. Feedback from method users will help verify that the methods are fit-for-purpose and are critical for gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author or methodfeedback@aoac.org. DOI: 10.5740/jaoacint.15-0260

03/10/2019