Charlotte Jacobsen, senior scientist at the Danish Institute for Fisheries Research, recently demonstrated that it is possible to eliminate the bad taste that the fish oil generates.
She concluded that the solution in the case of mayonnaise is the addition of the synthetically manufactured substance EDTA (Ethylene Diamine Tetra-acetic Acid). The substance is a metal chelator and serves as an antioxidant by removing, binding and inactivating tracer metals like iron - that otherwise would contribute to oxidation and thereby the development of the unpleasant taste.
Since the early 1990s Jacobsen has been investigating what makes products like mayonnaise, margarine and milk turn rancid, and consequently develop a harsh taste of train oil. Her recent findings has likely taken the body of knowledge of fish oil - full of omega-3 fatty acids believed to help reduce the risk of cardiovascular disease - further.