Influence of seasonal conditions on the composition and quality parameters of monovarietal virgin olive oils

The aim of this work was to determine the effect of the climatological conditions of the olive crop season on the composition of monovarietal virgin olive oils obtained from the Arbequina cultivar with special emphasis on the phenolic fraction, its percent distribution, and related oil quality parameters such as oxidative stability and bitter index. The main differences were due to freeze injuries caused by low temperatures in December 2001. The levels of chlorophylls and carotenoids in olive oil or pulp from frost-damaged olive trees were lower as a consequence of faster ripening. The olive oil extracted from frost-damaged olive pulp had lower contents of secoiridoid and especially lower levels of 3,4-DHPEA-EDA (the dialdehydic form of elenolic acid linked to hydroxytyrosol). In the following crop seasons, a significant increase in phenolic compounds, especially in secoiridoid derivatives such as 3,4-DHPEA-EDA, was observed. This increase may be due to the fact that olive trees that suffered frost damage in December 2001 were more sensitive to stress caused by the water deficit during summer in the subsequent crop seasons, which is usual in this olive-growing region. Moreover, important correlation coefficients were observed between the main secoiridoid derivative compound (3,4-DHPEA-EDA) and oxidative stability and the bitter index.