Tree Age Effects on Chemical Composition of cv. Verdeal Transmontana Olive Oil: Young vs Centenarian Trees

Introduction: Olive oil composition is influenced by multiple factors, including cultivar, climatic conditions, agronomic practices, and fruit maturation stage. Although olive trees undergo significant physiological and metabolic changes throughout their long lifespan, the influence of tree age on olive oil quality remains relatively unexplored. This study aimed to evaluate the influence of olive tree age on the chemical composition and bioactive properties of olive oils from the Portuguese cv. Verdeal Transmontana.

Material and methods: Olive oils were obtained from three age groups of olive trees: young (≤25 years), middle-aged (≤50 years), and centenarian (≥100 years), all grown under the same agronomic and environmental conditions in Mirandela (northern Portugal). Sampling was carried out over four consecutive crop years (2022-2025). The olive oils were analyzed for physicochemical quality parameters, antioxidant activity, oxidative stability, fatty acid composition, tocopherol profile, and hydroxytyrosol and tyrosol derivatives.

Results: All samples complied with the legal standards for extra virgin olive oil. Although significant differences were found among tree age groups, the crop year exerted a stronger overall influence on most parameters. Olive oils from centenarian trees exhibited higher oleic acid content (80.0 %) and lower polyunsaturated fatty acids (3.1 %). These olive oils exhibited higher total phenolic compounds, including hydroxytyrosol derived, contributing to enhanced oxidative stability and bioactivity. In contrast, olive oils from younger trees showed higher polyunsaturated fatty acids (5.5 %) and tocopherol content (459 mg/kg). Principal Component Analysis (PCA) enabled clear separation of samples, primarily driven by antioxidant activity, oxidative stability, tocopherols, and phenolic compounds. Linear Discriminant Analysis (LDA) further confirmed the discriminatory power of tree age on olive oil composition.

Conclusion: Olive tree age influenced the composition of cv.Verdeal Transmontana olive oils, but interannual variability had a greater overall impact, highlighting the predominant role of environmental conditions in olive oil quality.