ANTIOXIDANT ACTIVITY OF OLIVE LEAF, POMACE AND VIRGIN OIL EXTRACTS FROM PICUAL CULTIVAR AND THEIR HEAT AND pH STABILITY

Abstract

Antioxidant activity of olive leaf, olive pomace and olive virgin oil as affected by ethanol, ethyl acetate and chloroform solvents were evaluated. Ethanol extracts of olive leaf and olive pomace as well as chloroform extract of olive virgin oil had higher antioxidant activity than those from other solvents. Leaf ethanol extract and α-tocopherol had the similar antioxidant activity. Pomace ethanol extract had a higher (p ≤ 0.05) antioxidant activity than that of α-tocopherol however; virgin oil chloroform extract had a lower (p ≤ 0.05) antioxidant activity than that of α-tocopherol. Antioxidants of leaf ethanol extracts were heat-stable with retaining 67.04, 74.15, and 75.60% of its activity after dry heating at 100°C for 30 min, boiling at 100°C for 35 min and autoclaving at 121°C for 30 min, respectively. Antioxidants of pomace ethanol extracts were fairly heat-stable with 57.71, 63.75, 51.73% activity after dry heating at 100°C for 30 min, boiling at 100°C for 35 min and autoclaving at 121°C for 30 min, respectively. Antioxidant activities of leaf ethanol extract, pomace ethanol extract and virgin oil chloroform extract extracts were the maximum at pH 5.5. The induction periods of sunflower oil with 1% pomace ethanol extract, leaf ethanol extract and virgin oil chloroform extract were increased by 42.22, 35.56 and 16%, respectively as compared with the control sunflower oil. Pomace ethanol extract and leaf ethanol extract might be promising sources of natural antioxidant to be used in food products.