GreenLight for expanded microbial contamination detector

November 16, 2013

Mocon has expanded its food safety system that can reduce bacterial detection times for food processors and packers.

The indicator organism testing platform can test for enterobacteriaceae and total coliform counts using an oxygen depletion sensor and automated reader.

GreenLight microbial detection reduces test time by up to 60% compared to traditional tests that use culturing on Petri dishes, claims the firm.

The GreenLight system is configured to allow quantitative data and pass/fail testing in a fully automated mode.

This allows the user to set a pass/fail limit and be warned of failures in a shorter time than traditional plate count methods—which require 24-72 hour incubation time regardless of bacterial load.

Quicker test results

Food processors will benefit from quantitative test results in 10 hours or less, compared to the 24 hours required by traditional methods.

The system works by providing an aerobic plate count (APC) or total viable count (TVC) of a food sample’s microbial load by using a sensing assay or vial. As bacteria in the test sample multiply and respire, they consume oxygen.

The change in oxygen is used to calculate the original sample’s colony forming units per gram (CFU/g) for solids or per milliliter for liquids.

GreenLight microbial detection platform already had total count testing capability

Dairy target

Target applications include dairy, cheese and meat, Alan Traylor, business manager, microbial detection told

“Take a milk sample for example, divide the sample in two, add a nutrient buffer liquid to both and a selective media one of them.

“Then load both test vials into the GreenLight reader, click on the software screen and wait until readings are displayed on a computer monitor. The result is a Total Count and a Total Coliform count in about eight hours for a load of 1000 Colony Forming Units per millilitre.”

GreenLight 930 can test 48 samples continuously under full automation and can be adapted to test a maximum of 432 samples.

GreenLight 910 can read one test at a time in a smaller and less expensive way aimed at smaller food processing applications.

Traylor said the quicker the test results, the faster food processors can make decisions regarding the use of perishable incoming raw materials and outgoing products.

“Indicator organisms are families of bacteria that are similar to those that reside in human or animal digestive systems. A count of bacteria from these organism indicates the possibility of potentially harmful bacteria in a food sample.”

Asked how the oxygen depletion sensor and automated reader works, he said: “A polymer is integrated into a vial that can be loaded with a food sample. This polymer fluoresces when activated by light and the level of fluorescence changes as oxygen level changes.

“As aerobic bacteria grow, replicate and breath they consume oxygen and the sensor can then use an algorithm to deduce the bacterial load in the sample.”

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