Olive Treasures: Unveiling Fruit and Oil Characteristics of Aegean Region Varieties in Turkish Germplasm Bank

Abstract

This study comprehensively evaluated the fruit and oil characteristics of 26 olive genotypes from 2016/17–2019/20. The research focused on physicochemical quality parameters and purity criteria to classify the oils as extra virgin olive oil (EVOO) and explore their genetic and biochemical diversity. All analyzed oils met EVOO standards for free acidity (≤ 0.8% oleic acid), peroxide value, and UV absorbance (K₂₃₂, K₂₇₀), except one sample (Ters Yaprak). Phenolic content ranged widely (160.40–738.94 mg CAE/kg oil), correlating with oxidative stability (6.00–20.80 h). Oleic acid (65.29%–76.88%) and linoleic acid (5.63%–15.10%) were the dominant fatty acids, with variations linked to cultivar and climate. Total β-sitosterol (93.59%–96.55%) and Δ7-stigmastenol (0.18%–0.72%) were key markers for authenticity, though two samples exceeded Δ7-stigmastenol limits. α-Tocopherol (159.91–423.48 mg/kg) was the primary antioxidant, with Memecik, Ayvalık cultivars showing high levels. Phenolic content strongly influenced these attributes. Principal Component Analysis (PCA) revealed that phenolic content, oxidative stability, and fatty acid composition were the primary discriminators among cultivars. PCA results showed that variation in fatty acid, TAG, sterol compositions across 26 olive genotypes from 2016/17–2019/20 was primarily driven by genotype and harvest year, with no strong geographical clustering but distinct profiles for certain varieties such as Domat, Uslu, and Eşek Zeytini. Olive Varieties of the Aegean Region demonstrated exceptional quality, meeting EVOO standards with high phenolic and tocopherol content. Notable varieties such as Memecik, Ayvalık exhibited superior oxidative stability underscoring their commercial and nutritional value. This study provides critical data for conserving genetic resources and promoting regional olive oils in competitive markets.