Removal of dioxins and PCB from fish oil by activated carbon and its influence on the nutritional quality of the oil

Fish oils are well-known sources of nutritionally valuable components such as the n-3 FA EPA and DHA as well as the fat-soluble vitamins A, D, and E. However, some fish oils can be contaminated with considerable amounts of dioxins and dioxin-like PCB. The most important challenge during fish oil refining is to remove these contaminants without altering the levels of nutritionally valuable compounds and the oxidative status and stability of the oil. Treatment with an apolar adsorbent, e.g., activated carbon (AC), seems to be the most efficient process today. Very little information about the adsorption of different dioxin and PCB congeners is available. Four grades of AC were evaluated for their efficiency in removing these compounds. In addition, the effects of the treatment on the nutritional and oxidative quality of the oil were evaluated. After treatment of contaminated cod liver oil [5.4 ppt toxic equivalents (TEQ) polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F), 18.1 ppt TEQ dioxin-like PCB] with 0.5% AC, almost all PCDD/F and up to 80% of the dioxin-like PCB could be removed. AC showed low affinity for mono-ortho PCB (< 30% removal), which could be explained by their noncoplanar structure. Removal efficiencies were dependent on the grade and percentage of AC used. The treatment of contaminated cod liver oil caused no important effects on oil quality or FA composition in the conditions tested