Hot dogs labelled “beef” sold at a Malaysian market contained buffalo, according to a test that can detect tiny amounts of different species’ DNA.
The technique, developed by researchers in Malaysia, could be used to determine animal content in other meat products. And it isn’t limited to beef and buffalo – it works with many animals from rat to cat and cod to dog. The test was published in the Journal of Agricultural and Food Chemistry.
Finding out what’s in a hot dog isn’t a query too many of us would like answered. But, as we know, labelling and reality don’t always go hand in hand. Studies have found macaque meat in meatballs and dog in chicken nuggets.
Tainted meat products not only present a possibility that diseases might jump between species, but some cultural and religious beliefs prohibit consumption of various meats. (Also eating rat when you think it’s beef is just plain gross.)
Scientists can use DNA to see what animals are in a meat product. A sample of the product is crushed and mixed with solutions that extract DNA from the cells and amplify it. The extracted material is examined for strings of DNA, or combinations of, that are unique to a species.
The problem is the lengths of DNA can be very long, and can break apart during the mincing, heat-treating or cooking process.
So M. A. Motalib Hossain from the University of Malaya in Kuala Lumpur and colleagues wanted to find shorter strings of genetic material, which are less likely to break down, that could distinguish one species from another.
Meat contamination is a big issue in Malaysia, too. Around 60% of population is Muslim and another 6%, Hindu. Each has their beliefs about meat consumption.
So the team went to three markets and supermarkets and bought 16 types of meat, including cow, buffalo, pigeon and turtle. They also obtained samples of dog, cat, rat and monkey which had been killed to control the population.
They extracted the animals’ DNA and found short chains of DNA specific to each species.
To see how sensitive their test was, they made hot dogs with beef, buffalo and pork, but deliberately contaminated them with various amounts of other meats. These were boiled at 98C for 90 minutes.
And when they extracted the DNA from these custom-made hot dogs, they were able to detect contamination levels down to a minuscule 0.1%.
The next – and most interesting – step was to try to technique on commercial hot dogs. They bought 20 halal-branded hot dogs in Malaysian markets which were all labelled as “beef”.
They did indeed contain beef – but they also found “rampant substitution of beef with buffalo”.
The team also checked on the composition of chicken and pork hot dogs but none contained beef nor buffalo, probably because chicken and pork are cheaper meats.
The test, they write, is sensitive enough to be used by regulatory authorities for meat authentication.
But while it can tell us about the species of animal in hot dogs, they can’t tell what part of the animal is in there. To be honest, though, we’d probably prefer to be kept in the dark about that aspect.
Belinda Smith is a science and technology journalist in Melbourne, Australia.
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