Effect of olive fruit fly infestation on the quality of olive oil from Chemlali cultivar during ripening.

Olive fruits are seriously deteriorated by pre and post harvest damage due to the attack of insects, such as Bactrocera olaea, which strongly alters the quality of olives. Olives from Chemlali cultivar were collected and divided into different groups according to the presence or absence of infestation (0%, 5%, 10%, 15% and 100%) by the olive fruit fly (B. olaea). The infestation of this pest has been studied to evaluate its influence on virgin olive oil quality (free acidity, K(232) and K(270), fatty acids composition, pigment concentration, organoleptic characteristics, phenolic content, and antioxidant power). Results showed that both attacks by B. oleae and maturity process affected the quantitative and qualitative composition of the oil. These analyses demonstrated that the degree of fly attack was positively correlated with free acidity, the values of this parameter increase from 0.6 to 1.5 and 3.4, at the infestation levels 10%, 15% and 100%, respectively (R(2)=0.7418, P<0.05), and negatively related to the phenolic content which was always lower at the 100% infestation level (R(2)=0.9155, P<0.05), and consequently, the organoleptic characteristics. In addition, the infestation by olive fly did not cause an important change in the fatty acid composition while it is clear that fatty acids levels change in relation to the fruit repining stage. The antioxidant activity decreased during maturation, it was correlated to the total phenol content and the fruit infestation level.