Effect of plant extracts on the oxidative stability of sunflower oil and emulsion

The antioxidative activities of six plant extracts (catnip, hyssop, lemon b alm, oregano, sage and thyme) were evaluated in sunflower oil and its 20% o il-in-water emulsion in the dark at 60 degrees C. The oxidation process was followed by measuring the formation of primary (conjugated diene hydropero xides) and secondary (volatile compounds) oxidation products. Sage extracts (600 and 1200 ppm) effectively inhibited the formation of conjugated diene s and volatile compounds (hexanal and pentanal) in oil and emulsion and sho wed the highest antioxidative activity compared with 300 ppm BHT. Thyme and lemon balm extracts inhibited hexanal generation more than formation of co njugated dienes in both oil and emulsion. Oregano extract was more active i n oil than in emulsion. Catnip and hyssop extracts (600 ppm) showed prooxid ative action to sunflower oil at 60 degrees C. These two extracts increased the formation of conjugated dienes compared with the control oil. In emuls ions, catnip extract (600 ppm) was active and significantly inhibited the f ormation of conjugated dienes more than BHT (300 ppm) during additional inc ubation. (C) 1998 Elsevier Science Ltd. All rights reserved.