Effect of Foliar Pre-Harvest Calcium Application on the Mineral and Phytochemical Composition of Olive Oils ^†

Background: Several studies have investigated the possibility of using nutrients supplied as fertilizers to improve yield, firmness or final olive fruit size, however, scarce are the studies about the effect of pre-harvest foliar calcium application rate on mineral, quality and phytochemical composition of olive oils, which is the main goal of this investigation. Methods: For this study, an organic calcium compound (at two rates: 20 g/tree and 40 g/tree) and control (water) were applied to olive trees of three different cultivars (Cobrançosa, Galega, and Picual) at three different moments in a certified olive orchard in Portugal. At the commercial maturity, the olive fruits were harvested and processed to obtain the monovarietal olive oils. Results: The calcium application did not reveal significant changes on the quality parameters of the monovarietal olive oils, remaining extra virgin olive oils, however, the analysis of Ca mineral content revealed a significant increase of this content for some olive oil cultivars. Furthermore, some phenolic compounds concentration of olive oils were improved with the Ca foliar application, in opposite of antioxidant activity that was negatively affected. Conclusions: This investigation comes to demonstrate the cultivar effect on the final phytochemical composition, as well as the effect that Ca mineral content effect on the biosynthesis of bioactive compounds.