Nano label protects olive oil from counterfeiting

Falsification of premium oils is a major problem in the food industry, and researchers in Switzerland are offering a potential solution based on DNA-laced labels.

The silica-encased DNA labels can be added to premium-grade food products such as olive oil - as well as other high-value products such as petrol or Bergamot oil used in perfumery - in tiny amounts that resist detection.

The artificial DNA labels incorporate iron oxide nanoparticles that can be used to retrieve the labels using magnets in order to allow the product to be authenticated. 

Just a few grams of the label material would be enough to tag the entire olive oil production of Italy, says the development team from ETH Zurich, which has just published the work in the journal ACS Nano.

If counterfeiting is suspected, the particles added at the place of origin could be extracted from the oil and analysed, enabling a definitive identification of the producer. Experiments in the lab showed that the tiny tags dispersed well in the oil and did not result in any visual changes. They also remained stable when heated and weathered an ageing trial unscathed.

"The method is equivalent to a label that cannot be removed," says Robert Grass, lecturer in the Department of Chemistry and Applied Biosciences at ETH Zurich. "And with DNA, there are millions of options that can be used as codes."

The method also made it possible to detect adulteration, say the researchers. If the concentration of nanoparticles does not match the original value, another oil - presumably substandard - must have been added. 

The labels will have to pass toxicity and other testing before they can be used commercially in food applications, although ETH Zurich believes this should be fairly straightforward as the constituents are already used in foods. Silica particles are present in ketchup and orange juice, among other products, and iron oxide is permitted as a food additive E172.

It would also be possible to use natural rather than synthetic DNA - harvested for example from exotic fruits and vegetables - which could help alleviate any safety concerns, according to Grass, although he notes the risk from the labels should be weighed against the potential harm from adulterated foods.

"In the case of adulterated goods, there is no way of knowing what's inside," he said. "So I prefer to know which particles have been intentionally added."

The cost of label manufacture should be approximately 0.02 cents per litre.