Changes in phenolic content and antioxidant activity of Italian extra-virgin olive oils during storage.

Phenolic composition and antioxidant activity of extra-virgin olive oils extracted from several Italian varieties were studied at production and during storage. The antioxidant activity was measured according to the following tests: in the aqueous phase, by radical scavenging of the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation; and in the lipid phase, using the beta-carotene bleaching method. The phenolic content was not correlated to the oxidation indices (peroxide value and spectrophotometric constants). The phenolic contents and profiles of the various cultivars showed remarkable differences. The phenolic content was strongly correlated with the antioxidant activity measured according to the beta-carotene test and weakly correlated with the radical scavenging ability.