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Science helps to foil trade in imitation milk powder - 13/11/2012

New Zealand scientists have come up with an ingenious way to help identify fake milk powder being sold as a New Zealand product in overseas markets.

New Zealand exports about $2 billion worth of milk products to China each year, and a recent rise in imitation, and sometimes dangerous, dairy products in China has increased the importance of protecting the New Zealand brand.

Scientists at GNS Science at Gracefield and Otago University have completed preliminary work showing they can read milk powder’s geographical identification.

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We can also apply this type of science to other important problems, such as where insects and other biological material breaching New Zealand’s biosecurity have come from.

Dr Troy Baisden

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The scientists make use of the fact that New Zealand’s rainfall has a distinctive natural isotope signature that passes through pasture and into milk products. The two kinds of hydrogen atoms – or isotopes – naturally present in rainfall capture whether the rain fell in a warm or cold climate.

The ability to measure hydrogen isotopes in rainfall and biological materials, such as milk, has been advancing rapidly in the past decade.

Troy Baisden, of GNS Science, said progress was made possible by having the ability to look at the hydrogen isotopes in rainfall from each storm during the growing season when the milk is produced.

“We work with monthly rainfall samples from all over New Zealand. We turn information derived from these samples into a map of daily rainfall chemistry using climate data from NIWA,” Dr Baisden said.

Dr Troy Baisden, of GNS Science, has found that isotope analysis of rainfall collected on farms like this one in the  Wairarapa can help spot imitators trying to claim their milk products are from New Zealand.

Dr Troy Baisden, of GNS Science, has found that isotope analysis of rainfall collected on farms like this one in the Wairarapa can help spot imitators trying to claim their milk products are from New Zealand.

Otago University PhD student Emad Ehtesham carried out the research on the milk powder.

The technique involves using mass spectrometry in the University’s Chemistry Department to measure the ratio of the two hydrogen isotopes of bulk milk powder, or individual fatty acid compounds.

Associate Professor Russell Frew, of Otago University, said the technique opened the possibility of verifying the origin of the milk component of mixtures such as infant formula. Products such as butter and cheese might also be ideal applications for the technique.

The use of similar technology to verify the origin of whole foods was well established, Dr Frew said.

“The major advance here is that we are able to link the milk data to the rainfall map and hence use this to identify the origin of the commodity.”

Dr Baisden said the proof-of-concept work was very promising and was being developed further.

“We can also apply this type of science to other important problems, such as where insects and other biological material breaching New Zealand’s biosecurity have come from.”

The project to collect rainfall samples from all over the country was funded by the Government through Biosecurity New Zealand. Milk product samples were analysed at the University of Otago and maps made at GNS Science.