Removal of persistent organic pollutants in fish oils using short-path distillation with a working fluid

Abstract

Two fish oils, varying in origin, species and catching season, were decontaminated in a commercial scale short-path distillation equipment, aided by a working fluid (distilled ethyl esters of marine fatty acids). The processing conditions for the two oils varied by different processing temperature and pressure in the distillation column. The concentration of total cholesterol, vitamin E (alpha-tocopherol), vitamin A and vitamin D were reduced due to the decontamination process with the highest loss for the treatment with the highest temperature and lowest pressure (i.e. highest vacuum). Peroxide value (PV) and anisidine value (AV) were slightly reduced, and the content of the essential fatty acids EPA and DHA were reduced marginally. PCDD/PCDF, dl-PCB and ndl-PCB were efficiently removed with the highest efficiency for the treatment with the highest temperature (PCDD/PCDF, 76–96%; dl-PCB, 89–99%; ndl-PCB, 91–99%). For the treatment with the lowest temperature, the congeners were removed to varying degree, and there seemed to be a correlation between decontamination and the degree of chlorine substitution. Brominated flame retardants (PBDE) and chlorinated pesticides were only analysed in one of the oils (with highest process temperature). The overall decontamination efficiency was very high (PBDE, >86%, chlorinated pesticides, >89%). The short-path distillation, with working fluid, removes a broad group of persistent organic pollutants from fish oil efficiently with only minor negative effect on nutritionally important compounds.