3M Food Safety launches 24-hour aerobic bacteria indicator test
3M Petrifilm Rapid Aerobic Count Plates uses a dual-sensing indicator technology for enumeration of colonies in raw material, in-process and finished product food testing and environmental air, swab or surface contact testing.
Jason Semerad, global marketing manager at 3M Food Safety, said it has appeal for food processors and reference labs that need faster results to make time-sensitive raw material and/or product release, production and cleaning decisions.
It will also diminish the impact of spreader colonies known to cause difficult interpretation and costly retesting, he told FoodQualityNews.
Market possibilities
3M expects the test will be applied to segments including meats and poultry, fish, dairy products like cheese, raw milk, ice cream, yogurt, raw produce, vegetables, fruits, prepared and processed foods, dressings, and ingredients.
The aerobic plate count (APC) is intended to indicate the level of microorganisms in a product.
Procedures for determining the APC of foods have been developed by the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA).
Current agar based APC methods require 48 ± 2 hours incubation time.
The 3M system requires 24 ± 2 hours incubation time for most food matrices and environmental samples – the only exclusion is for dairy powders which has a time to result of 48 hours.
The sample-ready system uses a three-step process: inoculation, incubation and enumeration.
It contains nutrients, a coldwater-soluble gelling agent, and a dual-sensing indicator technology that facilitates colony enumeration. Incubation temperatures are 32°C or 35°C.
AOAC certification
The plate has received certification from the AOAC International Performance Tested Methods (PTM) program inserts.
Specific studies involved comparison tests to the FDA BAM and USDA reference methods and robustness and lot-to-lot/stability testing.
Semerad said it commissioned a study by the University of Minnesota Department of Food Science and Nutrition to compare performance at 30°C, 32°C or 35°C to the gold standard reference medium commonly used for aerobic bacteria, Standard Methods Agar (SMA).
“The study involved a total of 36 bacterial strains which included Gram (+) and Gram (–) bacteria,” he said.
“Quantitative results obtained on the 3M Petrifilm Rapid Aerobic Count Plates at 24 hours were comparable to those obtained on the Standard Methods Agar in 48 -72 hours, and the 3M Petrifilm Plate technology was found to provide significantly improved interpretation of results without sacrificing performance which is critical for food processors.”
Microorganism growth
Aerobic bacteria are present in oxygenated food matrices and serve as indicators of food spoilage.
The microorganisms can grow in a range of temperatures and pH values, so have the potential for causing substantial economic losses to the food industry, said Semerad.
“Getting accurate aerobic bacteria counts are critical to making time-sensitive decisions that ultimately impact process control, cleaning decisions, and product quality and safety,” he said.
“However, the 48-hour incubation required by traditional agar enumeration methods can prevent food producers from getting results in an actionable time frame.
“The 3M Petrifilm Rapid Aerobic Count Plate has technology that allows for easily counting colonies in 24 hours for most food matrices and environmental samples thus allowing actions in a plant to be taken a day earlier than traditional agar methods.”
The system was developed over 12 months with the first prototype tests in early 2014.
The nature of aerobic count tests include gram positive and gram negative organisms, said Semerad.
“Developing a method that can quickly and accurately grow both in half the time has been challenging. More specific organism tests, E.coli for instance, typically include specific additives to the growth media to grow E.coli bacteria and also to inhibit competing organisms from growing.”
