Fruit Ripening, Antioxidants and Oil Composition in Koroneiki Olives (Olea europea L.) at Different Maturity Indices

Harvest timing of oil olives is important for oil quality. Concerning the specific features of each cultivar, physiological and quality characteristics during ripening of Koroneiki olives were investigated in two successive years, A and B, from trees on full production. In A, olives were harvested at maturity indices (MIs) 0.9, 1.4, 2.1 and 4, while in B at MIs 1.1, 3.8 and 6.9. MIs similar to 1, similar to 4 and similar to 7 corresponded to green, red and dark purple peel in olives, respectively. Peel color parameters (L*, h degrees and C*), respiration and ethylene production rates were evaluated along with phenolic compounds and total antioxidant capacity (TAC) in olives of both crop years. Additionally, oil composition and a-tocopherol content were examined in olives harvested in years A and B, respectively. During fruit development, respiration and ethylene productions rates, hydroxytyrosol concentration and linoleic acid increased, while TAC, oleuropein, luteolin-7-O-glucoside, linolenic acid and alpha-tocopherol values decreased. Positive correlations were found among the attributes determined in both crop years that had a similar course of change during ripening, and vice versa, which could be also related to harvest timing and to quality traits of olive products. At MI similar to 4, at least all determined variables corresponded to oil of high quality. Practically, an early harvest might result in an olive fruit rich in antioxidants and therefore in oil production of high quality, high stability during storage and long self-life.

Automated summary

The harvest timing of oil olives is crucial for oil quality. This study investigated the physiological and quality characteristics of Koroneiki olives during ripening, and found that harvesting olives at a maturity index of 4 resulted in high-quality oil. Fruit development showed increases in respiration and ethylene production rates, as well as certain compounds, while total antioxidant capacity decreased. Positive correlations were found among the attributes determined, suggesting a relationship to harvest timing and quality traits of olive products.