Antioxidant potential of corncob extracts for stabilization of corn oil subjected to microwave heating

Antioxidant effectiveness of corncob extract with different polarity solvents (n-hexane, ethyl acetate, acetone, ethanol, and methanol) was assessed for total phenolics content (TPC), DPPH radical scavenging activity and % inhibition of peroxidation in linoleic acid system. The yield of the extracts from corncob with different solvents ranged from 1.1 to 19.5 g/100 g of dry matter. TPC, DPPH radical scavenging and inhibition of linoleic acid oxidation for corncob extracts varied significantly (P < 0.05) from 1.2 to 4.2, 16.0 to 42.1, and 37.3 to 89.9 g/100 g per dry matter, respectively. Methanolic extract offered the highest yield (19.5%), and also exhibited superior antioxidant activity. Corncob methanolic extract was added at concentrations of 500 and 1000 ppm to RBD (refined, bleached, deodorized) corn oil. BHT at 200 ppm served as standard beside the control. The stabilized corn oil samples subjected to microwave heating (0–21 min) were analyzed periodically. The magnitude of oxidative alterations was followed by the measurement of conjugated dienes (CD), conjugated trienes (CT), p-ansidine, and peroxide values. Results of different oxidation parameters revealed that methanolic extract at concentration of 1000 ppm was more effective than BHT and inhibited the rise in p-ansidine-, conjugated diene-, conjugated triene-, and peroxide-values up to 41.8%, 45.0%, 39.7%, and 65.0%, respectively, with respect to the control.However, at concentration of 500 ppm offered less efficient protection. The results of different antioxidant parameters investigated in the present study demonstrated that corncob is a potent source of natural antioxidants that might be explored to prevent oxidation of vegetable oils.