Determination of antioxidant effect of myrtle and thyme essential oils on some vegetable oils

In this study, thyme and myrtle essential oils were used to increase the oxidative stability of corn and sunflower oils. Thyme and myrtle (Myrtus communis L.) essential oils were added to sunflower and corn oils, 30% oil-in-water emulsions and frying oils at a rate of 100 mg/kg and their antioxidant properties were evaluated at the end of storage and frying process. It has been found that the oil most prone to oxidative degradation is sunflower oil, thyme and myrtle essential oils were effective in increasing and/or protecting the phenolic content and increasing antioxidant activity in sunflower and corn oils and oil-in-water emulsions during storage, and in frying oils during the frying process. After 21 days of storage at 60 °C, thyme essential oil was found to be effective in reducing peroxide value in sunflower oil, and myrtle essential oil in reducing TBA values in corn oil. In sunflower and corn oil-in-water emulsions, after 21 days of storage at 60 °C, the antioxidant effect of thyme and myrtle essential oil was pH dependent, and essential oils were found to be more effective in emulsions prepared at pH 3.4 and 5.4. In frying oils, it was found that after frying at 180 °C for 10 hours, myrtle essential oil was effective at reducing the peroxide value and TBA value, and especially in preventing darkening of the color. As a result, it was concluded that thyme and myrtle essential oils can be used as natural antioxidants in sunflower and corn oil, sunflower and corn oil emulsions with acidic character (pH<7) and in frying oils as a natural souces of antioxidants.