Direct quantitative indices for ripening of olive oil fruits to predict harvest time

The aim of this work was both the monitoring of selected indices, directly connected to biochemical phenomena of olive oil fruit ripening, and the processing of experimental results to choose the most appropriate harvesting time for olives. Two different olive cultivars (Frantoio and Moraiolo) in two different olive orchards were studied, picking olives by hand once a week from the beginning of September to the beginning of December. Olive samples were analyzed for average weight, pulp/stone ratio and Maturity Index. A homogeneous batch of olives was crushed, and the olive paste was used for the measurement of water, oil, sugar and phenolic compounds contents in olive oil fruits. Formally similar kinetics of oil and sugar contents were obtained for both studied cultivars and orchards. Oil contents showed an increasing sigmoidal trend tending to an asymptote; sugar contents showed an opposite behaviour with a decreasing sigmoidal trend tending to an asymptote. The total phenolic compounds content showed a decreasing trend during ripening. The secoiridoids oleuropein aglycon and oleuropein were among the most abundant phenolic compounds. Their contents showed a linear decrease during olive ripening, modelled by a significant pseudo-zero order kinetics; trends were cultivar-dependent, though similar for both orchards.