In most cases, fish oil is processed through chemical refining, a robust and flexible process that allows effective removal of impurities and free fatty acids (FFA). During this process, unwanted components are eliminated step by step through operations such as neutralization, bleaching and deodorization. This process is indispensable for fish oil processing where EPA and DHA preservation is the main objective.

For fish oils with less emphasis on EPA/DHA, Physical refining can be proposed instead of the chemical route. In physical refining, free fatty acids are removed during the deodorization step by steam stripping, typically resulting in lower product losses, especially for oils with higher FFA levels.

In both cases the refining is specifically adapted to deal with environmental contaminants. Depending on the origin, contaminants such as PCBs and dioxins, may need to be mitigated. This is important for food but even more important for fish feed and the fish farming industry where further concentration of contaminants could occur.

Many fish oils contain some high melting triglycerides, which affects the transparency of fish oil at ambient or colder temperature. When the emphasis is on the production of liquid and transparent oil, in most cases the fish oil is winterized, or fractionated. In this process, the higher melting, more saturated fraction is removed from the oil via fractional crystallization and subsequent filtration of the formed crystalline matter, in order to obtain a clear and brilliant fish oil. Similar as to winterizing and fractionation of vegetable oils, also fish oil fractionation requires specific crystallizer and filter designs, and a controlled cooling to maximize the filterability of the crystals.

A dry fractionation is less advisable in the case a large concentration of EPA/DHA is envisaged.

Desmet’s portfolio includes the specialized technologies for further processing of fish oils towards EPA/DHA concentrates. These technologies include transesterification to produce ethyl esters, or, urea complexation, as a first derivation to facilitate the concentration in a subsequent step to further concentrate these EPA/DHA derivatives, molecular distillation, dry fractionation or fractional distillation can be used. The concentrated EPA/DHA fractions can then be resynthesized into triglycerides, which is followed by a final refining as the last step.