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Authenticity of cheeses

Authenticity of cheeses

Scientists from the Quadram Institute on the Norwich Research Park have developed a test that differentiates between buffalo and cow’s milk, and between the cheeses made from them[7]. Buffalo mozzarella commands a premium price, compared to cows’ milk mozzerella, and is thus a target for fraudsters, either through mislabelling of cow’s milk mozzarella, or by partial substitution of buffalo with cows’ milk during production.

A team at the Quadram Institute has developed a new method for testing the authenticity of buffalo mozzarella. This work was carried out as part of the FoodIntegrity project, funded by the EU’s 7th Framework Programme for research and technological development. The test is based upon detecting slight differences between the ‘same’ protein from different species. It uses mass spectrometry, which allows very accurate measurement of the mass of molecules. Both buffalo and cows’ milk and cheese contain a protein called αs1-Casein, which differs between species by just 10 (out of >200) amino acids.

During sample preparation, the protein is broken down by an enzyme into shorter sequences of amino acids. The analytical test homes in on several distinctive ‘marker’ peptides which, due to the amino acid sequence differences, are characteristic of either buffalo or cow. Using Multiple Reaction Monitoring Mass Spectrometry (MRM MS), the marker peptides are selected by their masses, fragmented further, and the individual fragments are also analysed. This provides a very high level of sensitivity and specificity. Relative quantities of each in a mixture can also be measured accurately.

Applying the test to commercial products, the researchers found that two thirds of restaurant meals and supermarket pizzas claiming to be buffalo mozzarella were mislabelled, and instead contained mozzarella made wholly or partially from cows’ milk.

For most products, buffalo mozzarella is added as discrete pieces, so if it contains milk from mixed animal sources, then the adulteration is likely to have happened earlier in the supply chain. This means that the restaurants or supermarkets are also victims and possibly even the cheese producers themselves, if they are being unwittingly supplied with pooled milk from undeclared sources.  

References

7. https://quadram.ac.uk/buffalo-mozzarella-test/

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