Antioxidant synergy of α-tocopherol and phospholipids

The prevention of oxidation of a refined sardine oil by alpha-tocopherol at 0.04%, by several phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cardiolipin (CL)] at 0.5%, as well as by combinations of a-tocopherol with each phospholipid, was investigated. The evolution of the oxidation process during 1 mon at 40 +/- 2 degrees C was followed by a series of methods, measuring peroxide value (PV), diene, triene, and polyene index, and absorbance at 430 nm, while alpha-tocopherol and phospholipid content were being monitoried. Among these indices, PV was found to be the most adequate to follow the process. PC was the most effective individual antioxidant as shown by the PV values obtained at the end of the storage period, which were 54.0, 83.4, 87.9, and 97.7 meg O-2/kg for PC, CL, PE, and alpha-tocopherol, respectively. The highest synergistic effect was obtained with a mixture of alpha-tocopherol and PE, and the second and third best by mixtures made with PC and CL, respectively. The corresponding PV values recorded at the end of the period were 27.0, 35.0, and 58.0 meg O-2/kg. The high degree of synergy between PE and tocopherol is probably due to the occurrence of a simultaneous antioxidant mechanism involving Maillard compounds.