New Zealand scientists are hailing a breakthrough which could stop people from hijacking the country's lucrative dairy industry.
New Zealand exports $2 billion worth of milk products to China every year, but even more could be made if Chinese imitators were shut down, experts say.
"We have seen products that look like our own ones show up on Chinese websites from time to time and we know they're not ours because, in some cases, the packaging is a different shape or a different size, the colour is different and the spelling of the product might not be correct," said Nathan McKinlay from New Image Group.
Scientists believe they have found a way to sort the fake New Zealand milk from the genuine article.
The researchers, from GNS Science and Otago University, collect rainfall in different farming locations. These samples are then examined for natural elements which are transferred to grass, which is eaten by cows and ends up in the milk.
"Let's just say we find a package of milk powder in China and we want to know if it came from New Zealand.
"Now we can actually take it and track it and see if it matched the rainfall that happened in New Zealand when that milk powder should have been produced," said Troy Baisen from GNS Science.
This can also be used to find out if the milk came from the North or South Island.
Samples can be sent to a lab in Wellington, where scientists analyse them to check their hydrogen content. They can then match up the water samples with milk powder samples and work out which area of New Zealand the milk comes from.
It also hoped the science will protect more than just exporters, with baby formula the next item set to go under the microscope.