Antioxidative effect of extracts from red grape seed and peel on lipid oxidation in oils of sunflower

The antioxidative effect of red grape seed (RGS) and red grape peel (RGP) ethanolic extracts on primary and secondary lipid oxidation in sunflower and conjugated sunflower (SF/CSF) oils was evaluated. Lipid oxidation was analysed at 60 degrees C using three methods; conjugated diene (CD) measurements for primary oxidation product development, static headspace gas chromatography (SHGC), and proton transfer reaction-mass spectrometry (PTR-MS) to follow the formation of secondary lipid oxidation products (propanal, 1-penten-3-one, hexanal and octanal). The phenolic content (200 mg/kg) in extracts did not have any effect on the conjugated diene hydroperoxides. After 6 days, high antioxidative effect was found for the secondary oxidation products in CSF for peel extract followed by seed extract. The antioxidative activity for the peel extract was up to 41.2% for propanal measured by PTR as compared with 17.1 % for seed extract. On the other hand, at 6 days the peel and seed extracts were shown to expect prooxidative effect on SF for the secondary oxidation products. It has been noticed that SF has high stability for lipid oxidation among all the mixtures tested using the three determination methods. Obviously, PTR-MS succeeded, as an accurate method, to measure the concentration as low as 10 mu g/kg, and also to solve the solvent interference. (c) 2005 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved.