Isotope researcher Dr Karyne Rogers of
GNS Science.

A senior researcher at GNS Science has come up with a test that can verify if vegetables in the supermarket have been grown organically.

Karyne Rogers of GNS Science’s Stable Isotope Laboratory in Lower Hutt said the method was an inexpensive way to verify the organic status of vegetables by distinguishing between vegetables grown with organic or industrially made fertilisers.

A criteria in growing organic vegetables is that only organic fertiliser, usually animal manure, is used. As vegetables grow, they incorporate nitrogen from the fertiliser and it is this nitrogen which is analysed. The nitrogen isotope signatures of animal manure and industrial fertiliser are quite different.

 “It’s an independent check on the growing regime. As far as I am aware, this is the first simple reliable test for organic vegetables,” Dr Rogers said.

Clients can obtain results within 10 days of submitting samples, and the test can be done at any stage during vegetable growth. This method can also determine if vegetables are grown hydroponically, or naturally in soil.

A similar isotope technique using carbon can be used to determine if vegetables, such as tomatoes, have been grown in a greenhouse heated by fossil fuels.

Dr Rogers said these new tests were an extension of the food testing that the Stable Isotope Laboratory has been doing for the past 12 years.

“Since 1996 we have been testing orange juice for the beverage industry to determine if sugar or tap water has been added.”

 “We also offer a test for the honey industry to determine if bees have been fed sugar or if glucose has been added to increase the volume of the honey.”

Dr Rogers’ team is developing isotope-based tests that would determine if produce labelled “NZ Grown” was in fact grown in New Zealand.

Isotope analysis techniques offered the food industry a quick and reliable way to boost the confidence in labelling, Dr Rogers said.