As reported in Fig. 1, the olive lipase activity depends from the
fruit stage: an increase in enzymatic activity was observed during
ripening process with the maximumlipase activity at spotted II stage
and a lower value thereafter. These data are not in accordance with
previous studies, which demonstrated that themajority of the virgin
olive oils exhibit an increase in their titratable acidity (as a possible
result of lipase activity) during ripening and senescence progress.
Some exceptions are the olive oil obtained from c.v Villalonga olives,
which showed a slightly decrease of the free acidity, and the olive oil
extracted from cv. Lechìn [12], which acidity level remains constant.
In recent studies, analyzing virgin olive oil extracted from Ogliarola
cultivar, it was observed a slight, but not statistically significant,
increase in the amounts of FFAs when completely senescent
(blackened) olives were processed [5]. The reason for these apparently
conflicting indications may be that olives soften during fruit
ripening, then the riped fruits are more susceptible to mechanical
damages [15] and to fungal infection by e.g. G. olivarum, as demonstrated
by Mazuelos Vela [27]. In addition, lipase-positive yeasts may
grown in the olive paste during the malaxation phase and influence
negatively the quality of the oil determining the hydrolysis of the
triglycerides [6]; this suggests a limited role in TGAs hydrolysis for
the endogenous olive lipase. Moreover, it is interesting to note that
lipid formation in developing olive fruit shows a pattern similar to
that we have individuated for lipase [39].