Phenolic Profiles in Commercial Virgin Olive Oils Retain Cultivar Information Across Two Harvest Years

Phenolic composition of virgin olive oil is strongly cultivar-dependent, but its usefulness for cultivar differentiation may be limited by harvest year. This study evaluated whether phenolic profiles can differentiate oils of four cultivars, obtained from different commercial producers over two harvest years. The dataset comprised 164 variables derived from 19 identified phenolic compounds, including mass and molar concentrations, relative proportions, combined variables and ratios, and was analyzed using univariate and multivariate statistical methods. Numerous significant differences in phenolic composition were found among cultivars, and fewer between harvest years. Buža was distinguished mainly by higher pinoresinol and pinoresinol/1-acetoxypinoresinol ratio, Istarska bjelica by higher 1-acetoxypinoresinol, apigenin and oleuropein-derived aglycones, Oblica by high luteolin/apigenin ratio and high relative share of p-coumaric acid, and Leccino by lower relative share of p-coumaric acid, specific composition of oleuropein aglycones and higher vanillin. An LDA model with nine variables achieved cross-year accuracy above 90%, while PLS-DA identified markers most characteristic of each cultivar. Cultivar and growing region were partly confounded, as only Oblica originated from Dalmatia, while the other cultivars were from Istria. The cultivar-related differences retained in the two harvest years studied indicate good potential of phenolic profiles for classifying monocultivar virgin olive oils from the market.