Oxidative Stability of Virgin Olive Oil as Affected by the Bene Unsaponifiable Matters and Tertiary-Butylhydroquinone

During 16 h heating at 180 degrees C, the oxidative stability (OS) of virgin olive oil (VOO) as affected by the same concentrations (200 ppm) of tertiary-butylhydroquinone (TBHQ) and unsaponifiable matters of bene kernel (UKO) and hull (UHO) oils in terms of the inhibitory effect on the formation of conjugated diene hydroperoxides (OSCDV) and off-flavor carbonyl compounds (OSCV) was investigated. TBHQ was not able to considerably increase the OSCDV (7.51) of the VOO (7.2) and showed no synergistic effect with indigenous antioxidative compounds of the VOO (IOV) in this respect. However, it could significantly improve the OSCV (from 2.49 to 4.52), which was mainly due to its synergism with the IOV. The UKO increased considerably the OSCDV (to 11.8), and its OSCV (4.22) was nearly the same as that of TBHQ. The IOV still had marked contributions to the prevention of VOO oxidation but the majority of stabilizing effect was related to the UKO and its synergism with the IOV. The OSCDV in presence of the UHO was less than that of the VOO (5.96), although it significantly increased the OSCV (to 5.2), mainly due to the stabilizing effect of UHO and its synergism with the IOV.