Concentration and stabilization of n-3 polyunsaturated fatty acids from sardine oil

A simple and relatively inexpensive procedure to obtain 90% eicosapentaenoic acid + docosahexaenoic acid concentrates from sardine oil involved a two-step winterization of the oil (10 and 4 degrees C), followed by saponification and selective precipitation of saturated and less unsaturated free fatty acids by an ethanolic solution of urea. Antioxidant effects of butylated hydroxytoluene, dl-alpha-tocopherol and two natural antioxidants, quercetin and boldine, added to the concentrate (0.5% wt/vol), were compared in the Rancimat at 60 degrees C. dl-alpha-Tocopherol was unable to inhibit concentrate oxidation. Butylated hydroxyanisole and butylated hydroxytoluene had induction periods of 1.7-1.8 h compared to the control (1.0 h). A mixture of quercetin + boldine (2:1 w/w) significantly increased the induction period to 4.5 h.