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Yarok’s E. coli and Listeria modules validated by microbiology lab

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By Joe Whitworth+


Validation confirms results within time-frame of typical production shift. Picture: Yarok
Validation confirms results within time-frame of typical production shift. Picture: Yarok

Yarok Technology Transfer’s method to detect E. coli and Listeria monocytogenes in leafy vegetables has been validated by an Israeli microbiology lab.

The validation by the Institute For Food Microbiology (IFFM) was aimed at verifying the reliability of the technology and testing system.

It also looked at verifying whether it is implementable in industrial and commercial laboratories.

The procedure followed standards by the US Food and Drug Administration (FDA) and the European Pharmacopoeia (EP).

Yarok’s system is based on what it calls a ‘simple laboratory procedure’ and requires a proprietary system kit for fluorescence microscopy.

The kit contains proprietary reagents (growth media, markers), special filtration cups and slide holder for microscopy and dedicated software.

Knowledge to avoid a recall

The validation confirmed the testing method can provide reliable results for E. coli presence/absence in four and a half hours and for L. monocytogenes in eight to nine hours.

The system provides results after 45 minutes at a 1,000 CFU sensitivity (found in a traditional industrial standard sample of 25g).

This enables a producer to start evaluating options such as continuing production or stopping the line and taking corrective measures, said the firm.

Time to result (TTR) of rapid PCR systems for Listeria absence assessment are 36-42 hours and 18 hours for E. coli versus several days for traditional methods.

Jonathan Sierra, Yarok CEO, said currently test results are evident only after fresh products are marketed.

“By contrast, the validation procedure confirmed that our system delivers highly accurate results within the time-frame of a typical production shift. First clear results are provided in just 45 minutes,” he said.

“This short testing time enables producers to reliably evaluate raw material or final product conditions and deliverability, saving the industry on unnecessary costs, and drastically reducing the threat of product recalls. Results come in before products go out.

“In the case of leafy greens (or any other fresh product) a five hour time-frame is shorter than the length of a usual work shift. While the 18 hours waiting required by a rapid method is too slow, as the fresh product is expected to be delivered to the client distribution center or is already on the supermarket shelves or in the worst case, it has been eaten.”

Sierra added the focus on leafy vegetables (lettuce, rocket leaves, spinach, etc.) was due to the number of recalls and fatalities involving these greens.

Yarok said validation showed the method had a higher sensitivity (lower detection limit) than the reference analytical method in E. colipresence/absence tests, being able to provide count results for a single bacterium in the sample.

The method is based on intellectual property held by Dr Vladimir Glukhman, co-founder and chief scientist.

The false positive rate is 2% with the false negative rate at about 1%, said the firm.

Results are given on the interface by means of bacterial count: ‘00000’ will mean "Absence" a number higher than that means "At least one bacterium”.

The lowest Heterotrophic plate count (HPC) count is ≤10 CFU units, while the system can individuate less than ten bacteria and up to one bacterium when it provides a Zero/Absence result.

Development through partnerships

Yarok is developing more modules, while helping food producers (partners, early adopters) to solve a specific problem they may have and is not marketing the system at present.

FoodQualityNews covered one such installation at the labs of Agronomia Group last year.

“We plan to seek more partnerships with specific producers, in order to develop more modules addressed to other food sectors and/or modules for other types of vegetables ("non-leafy vegetables", such as carrots, zucchini, cucumbers, etc),” said Sierra.

“The system is made up of a core-technology and modules for specific food sectors and meanwhile, we continue with the general development of our start-up and of the technology, maybe for even faster results.”

Module indicates the "couple" matrix-to-be-tested and bacterium-of-interest.

The company’s module for Psychrotrophic bacteria in pasteurized milk testing is in use in the second largest dairy in Israel.

Later this year the firm plans to complete development of a module to detect Listeria in the production environment (surfaces, equipment, hands, clothing, etc.).  

This will be based on customised swabs, to take samples to be processed and examined with the core-technology.

“Listeria presence in the production facility is one of the main cause of product recalls in the US (the recall has to be announced even when the bacteria may not yet have been found in the product, but was found in the production environment),” said Sierra. 

“We believe we'll get a Listeria detection TTR similar (if not shorter) than the TTR just validated for leafy greens. This is a very short time and it may also be very useful in taking decisions regarding the periodic sanitation procedures every producer has to do day by day, week by week.”

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