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Thermus and the Pink Discoloration Defect in Cheese
Lisa Quigley1, Daniel J O'Sullivan2, David Daly2
1Teagasc Food Research Centre, Moorepark, Fermoy, Cork, Ireland; School of Microbiology, University College Cork, Cork, Ireland.
Msystems
|November 9, 2016
Summary
Pink discoloration in Continental-type cheeses is caused by the carotenoid-producing bacterium Thermus. This study identified Thermus in defective cheeses and recreated the pink defect by adding Thermus thermophilus, offering new strategies for the dairy industry.
Area of Science:
- Food Microbiology
- Dairy Science
- Bacterial Genetics
Background:
- Continental-type cheeses can exhibit a pink discoloration defect, causing significant financial losses.
- The microbial cause of this defect has remained unknown despite extensive research.
Purpose of the Study:
- To identify the microbial agent responsible for pink discoloration in Continental-type cheeses.
- To investigate the link between bacterial composition and the pink defect using advanced sequencing techniques.
Main Methods:
- 16S rRNA gene sequencing and shotgun metagenomics were used to compare bacterial communities in defect-associated and control cheeses.
- Quantitative PCR (qPCR) was employed to quantify specific bacterial genera.
- Culture-based methods were used to isolate and identify bacteria from defective cheeses.
Main Results:
- The genus *Thermus*, known for carotenoid production, was found at significantly higher levels in cheeses with pink discoloration.
- *Thermus thermophilus* was successfully isolated from defect-containing cheeses.
- Reintroduction of *T. thermophilus* into test cheeses recreated the pink discoloration defect, confirming its role.
Conclusions:
- *Thermus thermophilus* is identified as the causative agent of pink discoloration in Continental-type cheeses.
- This finding provides a basis for developing strategies to prevent this costly dairy defect.
- The applied molecular methods offer a framework for investigating other food defects of microbial origin.
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