Fourier transform infrared spectroscopy-chemometric approach as a non-destructive olive cultivar tool for discriminating Portuguese monovarietal olive oils

Four Portuguese monovarietal olive oils (cvs. Cobrancosa, Madural, Santulhana and Verdeal Transmontana) were evaluated, totalizing 24 independent samples. Olive cultivar significantly influenced (P values < 0.05, one-way ANOVA) the oils’ physicochemical and sensory attributes, fulfilling all oils the legal thresholds for extra-virgin classification. Oils from cv. Verdeal Transmontana had the highest oxidative stability (16.9 ± 1.0 h), whereas cvs. Cobrancosa and Santulhana oils have the highest total phenols content (204 ± 30 and 177 ± 33 mg GAE/kg, respectively). Concerning the sensory attributes, only cv. Santulhana oils fitted fruity greenly oils type, presenting, in general, significantly higher olfactory and gustatory intensities (P values < 0.05, one-way ANOVA), with a higher number of perceived sensory attributes (e.g., herbaceous sensations), compared to the other monovarietal oils. Free acidity, peroxide value, extinction coefficients, total phenols and oxidative stability allowed the unsupervised differentiation (principal component analysis, PCA) of the four monovarietal oils, and in a less extent, the sensory data. Fourier transform infrared (FTIR) spectroscopy-chemometric procedure was developed based on raw or transformed forms of the recorded spectra. Raw, 1st and 2nd derivative spectra allowed the unsupervised (PCA) and supervised (linear discriminant analysis, LDA) identification of the olive cultivar of the studied oils. In fact, FTIR-LDA models, based on the raw transmittance or on their 1st or 2nd derivatives, recorded at 5, 4 or 3 selected wavenumbers, respectively, allowed to correctly classify all oils (sensitivities greater than 99 ± 7% for the repeated K-fold-CV internal validation). Therefore, FTIR spectroscopy could be used as a fast, reliable, environmentally friendly and non-destructive olive cultivar-classification tool for monovarietal oils.