The use of olive leaves and tea extracts as effective antioxidants against the oxidation of soybean oil under microwave heating

Vegetable oils are prone to oxidative processes which lead to quality and nutritional losses, particularly under microwave heating, increasingly used in culinary procedures. Natural antioxidants can be regarded as good strategies in the inhibition of oxidation during culinary processing. In this work the addition of white tea and olive leaves aqueous extracts to soybean oil were evaluated as possible oxidative stabilizers during microwave heating (0-15 min; 1000 W). Microwave heating caused severe quality, nutritional and compositional losses, mainly beyond three minutes of heating, with marked increase in peroxide value, K-232, and K-270. Olive leaves extracts increased the vitamin E availability in the samples, were able to reduce the formation of oxidation compounds, and exhibited a higher protection against polyunsaturated fatty acids loss. White tea extracts provided higher antioxidant activity and oxidative resistance to the soybean oils. The use of natural antioxidants could be an effective way to protect soybean oil, one of the most important world crops, from oxidation. (C) 2012 Elsevier B.V. All rights reserved.