A new way of testing for the presence of horse meat has been developed by scientists in Britain.
The technique, developed by researchers at the Institute of Food Research, exploits subtle differences in a key meat protein.
The addition of just 1% of horse into a beef burger or of beef into lamb mince is now easy to spot, according to the research team based at the Norwich Research Park.
The technique also provides an estimate of how much unlabelled meat is illegally concealed in the product.
The red colour of meat is due to a protein called myoglobin. Proteins are made up of “building blocks” called amino acids, and, for example, the myoglobin of beef differs from that of horse by 18 amino acids.
This means that if the beef and horse proteins are broken up in the same way, researchers can detect these small differences in amino acid composition by measuring the respective mass of protein fragments within a sample.
This is the basis of the new test. Protein extracted from a meat sample is chemically chopped into fragments, called peptides, using an enzyme. The peptide soup is fed into a mass spectrometer that is tuned to measure the masses of only a handful of selected peptides.
If a burger contains only beef then only beef peptides will appear. But if a little horse meat has been slipped in then some horse peptides will show up too.
The relative hit rate of the horse and beef peptides give an estimate of how much horse meat has been added.
The entire procedure takes around two hours.
A report on the work, led by Dr Kate Kemsley, appears in the September issue of the Journal of Visualized Experiments, the world’s first peer reviewed scientific video journal.
The research was described in more detail in a paper in the journal Analytical Chemistry, and was funded by the Biotechnology and Biological Sciences Research Council.
Though so far demonstrated using raw meat from just four species, the team has also shown that key marker peptides persist in supermarket products, including for lamb in ready-curry and for beef in canned corned beef.
The scientists are therefore confident they can reveal meat adulteration in cooked retail products, of key interest to consumers and producers alike.
The institute’s researchers have teamed up with researchers in Stuttgart and Gdansk to extend this technique into other more complicated food products based on a suite of protein targets.
The testing of meat and food products for meat sources not revealed on the label has been the subject of considerable research since Europe was enveloped in a horse-meat contamination scandal in 2013.
Reports of the first cases of contamination of beef with horse meat arose in Ireland in January, but testing across Europe went on to reveal the scale of the problem.
Ready-made meals were pulled from supermarket freezers across the continent as a result.
Evidence emerged of forged invoices, labels and declarations intended to disguise the use of horse meat in beef products.
In all, 50,000 tonnes of meat products were recalled across Europe.
Subsequent investigations across Europe revealed the complexities of the food chain and its vulnerability to rogue traders.
Gunning, Y., Watson, A. D., Rigby, N. M., Philo, M., Peazer, J. K., Kemsley, E. K. Species Determination and Quantitation in Mixtures Using MRM Mass Spectrometry of Peptides Applied to Meat Authentication. J. Vis. Exp. (115), e54420, doi:10.3791/54420 (2016).
Meat Authentication via Multiple Reaction Monitoring Mass Spectrometry of Myoglobin Peptides, Andrew D. Watson, Yvonne Gunning, Neil M. Rigby, Mark Philo, and E. Kate Kemsley, Analytical Chemistry 87 (20), 10315-10322 doi: 10.1021/acs.analchem.5b02318