Oxidative Stability and α-Tocopherol Retention in Soybean Oil with Lemon Seed Extract (Citrus Limon) under Thermoxidation

The synergistic effect of lemon seed extract with tert-butylhydroquinone (TBHQ) in soybean oil subjected to thermoxidation by Rancimat was investigated, and the influence of these antioxidants on alpha-tocopherol degradation in thermoxidized soybean oil. Control, LSE (2,400 mg/kg Lemon Seed Extract), TBHQ (50 mg/kg), Mixture 1 (LSE + 50 mg/kg TBHQ) and Mixture 2 (LSE + 25 mg/kg TBHQ) were subjected to 180 degrees C for 20 h. Samples were taken at time 0, 5, 10, 15 and 20 h intervals and analysed for oxidative stability and alpha-tocopherol content. LSE and Mixtures I and 2 showed the capacity of retarding lipid oxidation when added to soya oil and also contributed to alpha-tocopherol retention in oil heated at high temperatures. However, Mixtures I and 2 added to the oil presented a greater antioxidant power, consequently proving the antioxidants synergistic effect.