Novel approach to study oxidative stability of extra virgin olive oils: importance of alpha-tocopherol concentration.
The stability of extra virgin olive oils is mainly due to their relatively low fatty acids unsaturation and to the antioxidant activity of some of the unsaponifiable components. We studied the activity of alpha-tocopherol in extra virgin olive oil in its natural state, using new and simple oxidizing conditions in "thin layer" and "bulk phase". Oxidation time course was monitored at 37 degrees C or 75 degrees C. A storage test was also performed. Two parameters were evaluated: depletion of alpha-tocopherol and formation of PUFA hydroperoxides, measured as conjugated dienes (CD) and peroxide value. The value of complex polyphenols was also measured. alpha-Tocopherol concentration decreased in function of time and temperature and showed a strong inverse correlation with the increase of CD. When alpha-tocopherol reached a "threshold value" of 60-70 mg/kg, a significant increase of CD formation was observed, together with a good correlation between CD and peroxide value. The initial amount of alpha-tocopherol is one of the components that influences oil oxidative susceptibility.
Deiana
Monica
M
Dip. di Biologia Sperimentale, Sez. di Patologia Sperimentale, Università degli Studi di Cagliari, Cittadella Universitaria, KM 4.5 SS554, 09042 Monserrato (CA), Italy. mdeiana@unica.it
Rosa
Antonella
A
Cao
Clara Falqui
CF
Pirisi
Filippo M
FM
Bandino
Giovanni
G
Dessì
M Assunta
MA
D000975:Antioxidants / Q000032:analysis*; D004355:Drug Stability; D007700:Kinetics; D000069463:Olive Oil; D010084:Oxidation-Reduction; D010938:Plant Oils / Q000737:chemistry*; D024502:alpha-Tocopherol / Q000032:analysis*
D000975:Antioxidants; D000069463:Olive Oil; D010938:Plant Oils; D024502:alpha-Tocopherol