13C nuclear magnetic resonance spectroscopic detection of the adulteration of extra virgin olive oils extracted from different cultivars with cold-pressed hazelnut oil.

13C NMR spectroscopy was applied to detect the adulteration of olive oils with hazelnut oil. Considering that the linolenate chain and the squalene hydrocarbon were absent in hazelnut oil, unlike olive oil, a 13C NMR spectroscopy method was developed to measure in addition to the triglyceride normal chains (i.e., saturated, oleate, and linoleate chains), the resonances of the linolenate chain and of squalene hydrocarbon. Acyl chain and squalene resonances highly discriminated olive oil samples by cultivars. Nevertheless, the "hazelnut oil percentage factor" prevailed over the "cultivar factor," thus correctly classifying 86% of the authentic and adulterated olive oil samples according to the hazelnut oil percentages. In particular, 85.7, 73.7, and 100.0% of the authentic olive oil samples, and the samples adulterated with 5 and 20% of hazelnut oil, were correctly classified through cross-validation.