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Quantitative authenticity testing of buffalo mozzarella combats fraud.

Buffalo milk, which is used to produce mozzarella cheese, commands a premium price compared to cows' milk. Products labelled as buffalo mozzarella must be made only with buffalo milk, and not with milk from other species.

Mozzarella can also be made with cows' milk, but this is a much lower-priced product. So, buffalo mozzarella essentially has become a target for fraudsters, either by mislabeling cow's milk mozzarella, or by partially substituting buffalo with cows' milk during production.

To stay ahead of the fraudsters, scientists are improving the effectiveness of analytical techniques. They are using multiple reaction monitoring (MRM) and mass spectrometry to detect and quantify bovine milk in buffalo mozzarella cheese. The test focuses on the abundant protein [[alpha].sub.s1]-casein, present in buffalo and cows' milk and cheese, but with 10-amino acid-sequence differences.

The researchers extract a list of marker peptides specific to each species. Identical peptides, exactly the same in both species, are used for relative quantitation of the casein in each type of milk. Similar peptides, present in both species but differing typically by one amino acid, demonstrate relative quantitation in binary cheese mixtures.

During sample preparation, the protein is broken down by an enzyme into shorter sequences of amino acids[??] peptides. The test focuses on several distinctive marker peptides which, due to the amino acid sequence differences, are characteristic of either buffalo or cow.

Using MRM mass spectrometry, the scientists select the marker peptides based on their masses. They are fragmented further, and the individual fragments analyzed, providing a very high level of sensitivity and specificity. Relative quantities of each in a mixture can also be measured accurately.

The scientists used their method on some retail mozzarella products. Eight samples of supermarket cheeses specifically labelled as buffalo were all found to be 100% buffalo. Five other samples, labelled mozzarella, were all 100% cow. These samples showed no signs of adulteration.

However, when the scientists analyzed other products labelled as containing buffalo mozzarella, a number were suspicious. Two-thirds of supermarket pizzas, restaurant pizzas and other restaurant dishes that claimed to be buffalo mozzarella contained at least some cows' milk. In some, the mozzarella was completely derived from cow. The test is available as an analytical service: https://www.qibextra.co.uk.

Further information. Kate Kemsley, Quadram Institute Bioscience, Colney Lane, Norwich, Norfolk NR4 7UQ, United Kingdom; phone: +441603 255000; email: kate.kemsley@quadram.ac.uk.

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Author:Kemsley, Kate
Publication:Emerging Food R&D Report
Date:Apr 1, 2019
Words:410
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