Process for separating polyunsaturated fatty acids from long chain unsaturated or less saturated fatty acids

A process for separating polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) from less saturated long chain fatty acids (LCFAs) in a lipid composition, wherein said PUFAs and LCFAs are present as (i) triglycerides, or (ii) free fatty acids or monoalkyl esters, by exchange of at least a portion of LCFAs with short and/or medium chain fatty acids (MCFAs). The process can suitably be employed on marine derived oil, marine oil 2 derived oil products and other sources of PUFAs, including PUFA-rich singe cell oils (SCOs), and oils from genetically modified organisms with a modified lipid metabolism. The inventive process is based on novel use of lipases and distillation techniques, selectively chemically modifying species in the substrate material such that the desired species and chemically similar species become sufficiently dissimilar to be separable. Thus PUFA can be effectively enriched from material such as 30 herring oil with low PUFA content and high content of equal length monounsaturated fatty acids such as 20:1 and 22:1 fatty acids.