Eicosapentaenoic acid alkyl ester-containing composition and method for producing same

A method for producing a composition comprising an eicosapentaenoic acid alkyl ester, the method comprising:

• preparing a raw material oil comprising from 50 to 92% by mass of an eicosapentaenoic acid alkyl ester in the total fatty acids, wherein a mass ratio of a docosahexaenoic acid alkyl ester to the eicosapentaenoic acid alkyl ester included in the raw material oil is 3.3% by mass or less, and a ratio of trans isomers in the eicosapentaenoic acid alkyl ester included in the raw material oil is 2% by mass or less;
• bringing the raw material oil into contact with an aqueous solution comprising a silver salt;
• recovering the aqueous solution;
• bringing the recovered aqueous solution into contact with an organic solvent;
• and
• recovering the organic solvent, thereby producing a composition comprising an eicosapentaenoic acid alkyl ester,
• wherein the produced composition comprising the eicosapentaenoic acid alkyl ester comprises at least 96% by mass of an eicosapentaenoic acid alkyl ester in the total fatty acids, and has a ratio of trans isomers in the eicosapentaenoic acid alkyl ester of 1.5% by mass or less.