Reading the fingerprints on your nuts

Not all hazelnuts Corylus avellana are equal. There are different varieties of hazelnut, and also differences in how they’re grown. Fountoúkiphiles say the very best hazelnuts come from Italy. Nuts from Azerbaijan only fetch half the price, so there’s an opportunity for suppliers who are willing to bulk up their shipments of Italian hazelnuts with cheaper supplies.

With twenty-five varieties of hazelnut consumed and many potential sources for nuts, identifying which nuts you have is a challenge. Thomas Hackl and colleagues have been working to find a technique that works with hazelnuts from anywhere.

The researchers ground up 262 nut samples from different regions around the world and extracted the metabolites, which they identified with proton Nuclear magnetic resonance (NMR) spectroscopy. This is a technique that uses varying magnetic fields to agitate electrons in a sample. By seeing what precise energies are needed to jolt the electrons, you can create a spectrum that identifies what you have in your sample. It’s a technique that’s already been used to analyse wine.

The spectra showed that nuts from different regions had different metabolite profiles, with certain compounds proving distinctive for specific areas. For example, the amount of betaine, an amino acid derivative, varied significantly in nuts from different countries. Using betaine as a marker could help build a rapid test for provenancing – however, it’s not perfect.

The team said of the test: “The best result in terms of country classification was obtained for Georgian samples, without misclassification. The samples from Turkey and France show equivalent results with 96% and 94% true positive rate (TPR), respectively. The lowest accuracy with 78% was obtained for the assignment of Italian samples. The highest false positive rate (FPR) occurs for Italian samples that were misclassified as Georgian and for German samples that were misclassified as French.” They suggest working with other tests, in order to improve confidence in the test results.

Source: Eurekalert.