Scientists at Teagasc and University College Cork (UCC) have identified a heat-loving bacterium as the cause of pink discolouration defects in cheese.

Pink discolouration affects many cheeses throughout the world and this leads to significant financial loss for the industry.

New research has now linked the pink defect in cheeses with the presence of a bacterium from the genus Thermus; a thermophile (heat-loving) microorganism that is more frequently associated with environments such as hot thermal springs and which is known for its production of vivid pigments including carotenoids.

DNA sequencing

The research, which was led by Dr Paul Cotter and Dr Diarmuid Sheehan, used high throughput DNA sequencing technologies.

The presence of Thermus was unexpected, and once researchers established this, they were able to employ specialised techniques to grow the bacteria on agar plates.

Subsequently, they artificially added the microbe back into an experimental cheese, and recreated the pinking defect. As a result, the role of Thermus in this defect was definitively established.

New strategies

The application of high-throughput DNA sequencing technologies means that it is now possible to study the microbiology of foods without the need to first grow the microorganisms present. According to Teagasc, this is particularly important in situations where key microorganisms are not easily grown, and would previously have been overlooked.

“This finding has the potential to lead to new strategies to eliminate this defect while also representing an approach that can be employed to investigate the microbial role in other food defects of unknown origin,” said Dr Paul Cotter, principal research officer, Teagasc Food Research Centre, Moorepark, and principal investigator, APC Microbiome Institute, University College Cork.

This research demonstrates the significant effect that DNA sequencing technologies are having on our understanding of, and ability to address, food quality- and food safety-related issues.”

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