Reading the fingerprints on your nuts

Are you getting the hazelnuts you pay for? How do you know? A new technique offers an alternative to subjective tests like flavour.

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.

Hazelnuts
Hazelnuts. Are you getting what you pay for?

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.

Reference List

Bachmann, R., Klockmann, S., Haerdter, J., Fischer, M., & Hackl, T. (2018). 1H NMR Spectroscopy for Determination of the Geographical Origin of Hazelnuts. Journal of Agricultural and Food Chemistry, 66(44), 11873–11879. https://doi.org/10.1021/acs.jafc.8b03724

Godelmann, R., Fang, F., Humpfer, E., Schütz, B., Bansbach, M., Schäfer, H., & Spraul, M. (2013). Targeted and Nontargeted Wine Analysis by 1H NMR Spectroscopy Combined with Multivariate Statistical Analysis. Differentiation of Important Parameters: Grape Variety, Geographical Origin, Year of Vintage. Journal of Agricultural and Food Chemistry, 61(23), 5610–5619. https://doi.org/10.1021/jf400800d

Klockmann, S., Reiner, E., Bachmann, R., Hackl, T., & Fischer, M. (2016). Food Fingerprinting: Metabolomic Approaches for Geographical Origin Discrimination of Hazelnuts (Corylus avellana) by UPLC-QTOF-MS. Journal of Agricultural and Food Chemistry, 64(48), 9253–9262. https://doi.org/10.1021/acs.jafc.6b04433

Klockmann, S., Reiner, E., Cain, N., & Fischer, M. (2017). Food Targeting: Geographical Origin Determination of Hazelnuts (Corylus avellana) by LC-QqQ-MS/MS-Based Targeted Metabolomics Application. Journal of Agricultural and Food Chemistry, 65(7), 1456–1465. https://doi.org/10.1021/acs.jafc.6b05007