Can the region of production affect the quality and composition of olive oil? Comparative study on two olive cultivars

Portugal is a notable olive oil-producing country, gaining prominence in the last decade. This study examined how geographic origin influences olive oil quality by analyzing samples from three key regions (Alentejo, Beira Interior, and Trás-os-Montes) and two major cultivars: Cobrançosa and Galega. All oils met the extra-virgin classification criteria, with free acidity consistently below 0.30%, and peroxide values ranging from 2.3 to 6.7 mEq O₂/kg. Alentejo oils were sensorially more intense, showing higher bitterness and pungency (up to 6.1 and 6.8, respectively). Significant chemical differences were also observed: Trás-os-Montes oils presented the highest monounsaturated fatty acid content (up to 76% MUFA), whereas Alentejo showed the greatest concentrations of hydroxytyrosol-based compounds (up to 450 mg/kg) and strong antioxidant activity (DPPH inhibition up to 80%). Beira Interior oils exhibited the highest α-tocopherol levels (up to 428 mg/kg). Heatmaps and principal component analysis (PCA) revealed clear chemical differences based on origin, demonstrating that environmental factors significantly influence composition, oxidative stability, and antioxidant potential. These results highlight the role of terroir in shaping both the sensory and chemical properties of Portuguese olive oils.