According to the relevant European Union legislation, only those cheeses produced in a traditional way in some areas of Greece (mainland and the island of Lesbos), and made from sheep milk, or from a mixture of sheep and goats’ milk (up to 30%) of the same area, may bear the name "feta". Everything else should be called white cheese although similarly brined cheese products are found elsewhere in the Mediterranean region.
Similar brined white cheeses produced outside the EU are often made partly or wholly of cow's milk, and they are sometimes called feta. Not a legal problem if they are sold outside the EU, e.g. here in Canada, but inside it is illegal.
I admit I am one of those people that prefer the real feta or at least the one made from sheep milk. In Canada it is hard to get and if you do it costs a fortune (as most quality cheese). Instead you mostly get a cow milk alternative. This is not a big problem but if you are in the motherland of feta and you buy a product labelled "feta" you can expect the real stuff.
Well, researchers from the Institute of Agrobiotechnology at the National Center for Research and Technology Hellas (CERTH) in Thessaloniki showed that this isn't necessarily true. They used DNA Barcoding and were able to show that some products were mislabeled as they contained cow's milk, sometimes mixed with goat milk, but no sheep milk.
They also tested other products sold in Greece and developed markers to be able to identify local varieties of cherries, lentils and beans. On average they found 20% of the samples being wrongly labelled. Cheaper alternatives are sold as the more expensive product. Another product tested was basmati rice which in up to 50% of the cases turned out to contain Greek varieties of non-aromatic rice that are much cheaper.
As a consumer my first reaction to such findings is always anger although my experience tells me to expect this. However, news like this also raise the hope that matters will change as we do have the tools in place to find out the truth. We just need to apply them more often.