CSI: Supermarket
February 15, 2013
Food samples regularly undergo testing in Germany - and not just when food scandals dominate the headlines. For Claudia Brünen-Nieweler, a microbiologist with a regional animal research agency in Germany, testing different kinds of meat is a daily routine. "We test about 600 samples each year," she said of her agency.
The process starts with the food monitoring officials bringing various meat products from the supermarket to their laboratory - items like sausages, and frozen meals - including lasagna Bolognese, the focus of the most recent tainted food scandal that started in the United Kingdom.
Brünen-Nieweler determines whether the type of meat in the food actually reflects what is listed on the package. In order to do that, first the laboratory workers have to separate out the meat from the rest of the food, Brünen-Nieweler explained. This involves removing the sauce from the lasagna and running it through a sieve with water until only pieces of meat remain.
Copy and compare
The meat is then pureed and mixed with special enzymes and chemicals that break down the cell walls. DNA is found in the cell nucleus, and can only be extracted through this elaborate procedure.
The scientists obtain a tiny amount of genetic material, which is used in the next part of the process: the polymerase chain reaction. This technical process generates many copies of the subject DNA sequence, allowing for definitive identification on what kind of animal the meat came from.
This process is also used in paternity tests as well as murder trials. The suspect's DNA, found at the scene of a crime or on a corpse is replicated and compared with a known sample.
Brünen-Nieweler said the replication process takes about two hours. After that, it's clear whether the meat in question is pork, beef, goat, sheep - or horse. Using the polymerase chain reaction process, it's possible for a laboratory to exactly determine whether lasagna Bolognese contains beef, as it should, or rather some other kind of meat. But the test doesn't prove how much - "we can only say, a lot or a little," Brünen-Nieweler added.
The method also works for other animal products, such as milk, cheese or yoghurt. Each test takes about two days to complete, and costs about 140 euros ($187).