Prepared Foods

Versatile microbiology system streamlines quality control

Versatile microbiology system streamlines quality control – food sample tester

Versatile microbiology system streamlines quality control

During the 1970s, researchers with Canada’s Health Protection Branch (akin to the Food and Drug Administration in the U.S.) developed some novel and dynamic concepts on how to improve food microbiology. QA Laboratories was established in 1979 to develop these ideas into useful products for the food microbiologist.

In QA’s research facility in Toronto, its microbiologists and product development specialists produced the ISOGRID microbiology system.

ISO-GRID, now officially recognized in the U.S., Canada and Japan, is “probably the most diversified method in existence in terms of its breadth of application,” according to Mike Entis, vice president at QA Laboratories. It can be used to test food samples for a raft of organisms such as coliforms, listeria, salmonella, yeast and mold by altering the culture medium.

Best Foods uses the ISO-GRID system in all of its U.S. manufacturing plants to test a wide range of food products and ingredients for total microbial counts and specific organisms such as E. coli and Staphylococcus aureus. ISO-GRID has allowed the company to standardize its testing methods, and it has decreased material needs and significantly reduced analytical turn-around time, according to John Erickson, research associate microbiologist at Best Foods’ Research and Engineering Center, Union, N.J.

Basic components of the test include a filtration unit, hydrophobic grid membrane filter (HGMF), toggle clamp that locks the HGMF into the filtration unit, and a line counter with a microprocessor guide. The filtration unit retains all particulate food matter on a sieve-like prefilter and allows the microorganisms to flow through to the HGMF, which is then placed on the appropriate culture medium for incubation.

The filtration unit allows you to test virtually any food product for almost any food organism. Best Foods uses ISO-GRID to test products ranging from highly acidic mayonnaise to dry foods (soups and sauces), syrups and starches.

“We went with this technology because it’s simple and easy to learn,” says Erickson. “It’s easy to integrate into your QC programs.” Companies using the versatile ISO-GRID system can screen food samples for different organisms by training lab personnel in just one procedure. The only conditions that change are the culture medium and incubation time and temperature.

For example, the ISO-GRID Opti-MUG method (approved by the AOAC earlier this year) uses two culture media to screen food samples for total coliforms and, specifically, E. coli. First, the filtered sample is incubated on lactose monensin glucuronate (LMG) agar for 22 hours. If coliform colonies are not present at that time, the test for both total coliforms and E. coli is complete. If colonies are present, the filter is transferred to buffered MUG agar (BMA) and incubated for two more hours. If E. coli colonies are present, they will fluoresce bright blue-white under long-wave ultraviolet light.

QA touts the OptiMUG system as “the only known test that will give confirmed results for both organisms in 24 hours without any further confirmatory steps.” ISO-GRID also tests for:

Salmonella. You can start this test anytime on Monday and get presumptive positives (if any) by Wednesday morning and confirmed positives by Thursday morning.

Aerobic plate count. By using just one ISO-GRID HGMF, you can eliminate multiple dilutions and increase reliability and reproducibility.

L. monocytogenes. Negative screen in three days. Presumptive positive colonies can be subcultured directly from the HGMF for confirmation.

Yeast and mold, and S. aureus. Results in 48 hours.

C. perfringens. Presumptive count in 24 hours. Confirmed count in 72 hours.

Y. enterocolitica. Negative screen in four days. Confirmation three days later. Total test time is seven days.

QA Labs also works with companies to develop customized media for specialized tests. The method is “limited only by the imagination,” says Entis.

Erickson points out that the media can be made into ready-to-use pour plates and, if stored under proper refrigeration, can be used over a period of two weeks without any decrease in microbiological sensitivity.

A disposable version of the ISO-GRID system is being introduced this month at the 1989 Institute of Food Technologists Expo (IFT). QA Laboratories.

PHOTO : The versatile ISO-GRID microbiology method can be used to test food samples for a raft of organisms such as coliforms/E. coli, listeria, salmonella, yeast and mold by altering the culture medium. Inset shows salmonella colonies on an ISO-GRID membrane filter.

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