New DNA tracking can identify bugs contaminating milk

A new system of DNA sequencing to track down and identify potentially dangerous bugs which contaminate milk and can cause illness in consumers has been pioneered by researchers at Teagasc and UCC.
New DNA tracking can identify bugs contaminating milk

A new system of DNA sequencing to track down and identify potentially dangerous bugs which contaminate milk and can cause illness in consumers has been pioneered by researchers at Teagasc and UCC.

“What we have done is to use an approach called high throughput DNA sequencing. We use the DNA in the micro-organisms to identify all the micro-organisms present in the milk as part of the same test,” explains Professor Paul Cotter, head of food biosciences at Teagasc.

Milk is such a nutritious environment, he explains, a variety of micro-organisms can grow in it:

“Different micro-organisms can enter milk at different stages of the productions process and if they can last long enough through the production process, some can spoil milk or cheese and some can be disease-carrying and make us sick,” he says.

Micro-organisms can enter the dairy processing chain at a very early stage, such as through mastitis in a cow, or later on if correct hygiene procedures are not maintained in a processing facility.

Examples would be the Pseudomonas microbe which copes well with cold temperatures, although pasteurisation will generally kill it.

“However, sometimes it can become problematic through post-pasteurisation contamination, producing enzymes which cause milk to spoil,” he explains.

Another microbe, Bacillus Cereus, can be very resilient to high temperatures and pasteurisation. If it survives through to the end product stage, it can result in illness in the consumer, such as vomiting or diarrhoea.

Traditional microbiology is currently being used to test for these and other undesirable microbes, Prof Cotter explains, adding however, that while these approaches are effective they can be time-consuming and slow, and are only capable of identifying the specific micro-organisms that are being tested for.

“This is a problem if an unusual microbe enters the milk or processing facility. It can remain undetected, as it is not being specifically tested for,” he observes.

What the researchers at Teagasc and UCC have now done, he explains, is to use an approach called high throughput DNA sequencing. The team recently published a paper in the peer-reviewed journal mSystems on ‘Tracking the Dairy Microbiota from Farm Bulk Tank to Skimmed Milk Powder’.

“We use the DNA in the micro-organisms to identify all the micro-organisms present in the milk as part of the same test,” says Prof Cotter, adding that the team anticipates that in the future there would be a cloud- capacity approach under which analysis could be carried out remotely and quickly and effectively.

The research was carried out through testing of real world milk samples collected from over 50 farms and at the various steps along the process until the resultant skim milk powder product was made.

This study also inspired the EU-funded MASTER project, led by Prof Cotter, through which this approach will be further developed through testing across 100 food processing companies around Europe.

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