Desmet’s fish oil processing is built around a series of refining and upgrading steps that can be combined and optimized depending on the quality of the crude fish oil and the intended food or feed application. The objective is to gradually remove unwanted components, while preserving valuable fatty acids and minimizing losses.

Chemical refining

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 unavoidable for fish oils where EPA and DHA preservation is the objective.

Physical refining

Some fish oils containing low EPA/DHA, or oils intended for applications where preservation is less important, can be refined physically. In this route, 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. These oils can also be hydrogenated and interesterified, and may contribute to certain functional properties.

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 there is a further concentration effect.

Dry fractionation

Many fish oils contain some high melting triglycerides, sometimes referred to as stearin, which makes the oil semi-solid at ambient temperature. In such cases the fish oil is winterized or better fractionated. In this process, the high melting fraction is removed from the oil, to obtain a clear liquid fish oil.
Unfortunately, this process is not very effective in concentrating EPA/DHA though there is some effect. However, fish oil fractionation requires some specific process design to be effective.

EPA/DHA concentrates

Desmet has a wide portfolio for further processing of fish oils. Fish oils can be processed to obtain EPA/DHA concentrates. It includes transesterification to produce ethyl esters or urea complexation.

To further concentrate EPA/DHA derivatives, molecular distillation, dry fractionation or fractional distillation can be used. Recomposing triglycerides and final refining are applied as final steps.

For premium products, molecular distillation is the preferred option for concentrating EPA and DHA, as it allows selective separation and to process at low temperature and avoiding EPA/DHA degradation, operating under deep vacuum and low temperatures.

Molecular distillation could be used to produce a pre-concentrate but not recommended for high end products.