Cryo-FIB SEM for Characterization of the Structure of Fish Oil Emulsions

Addition of fish oil to food products to improve nutritional quality by the addition of omega-3 fatty acids is attractive both to the consumers and the food industry for reasons such as health benefits and added product value. The long chain omega-3 fatty acids contain a large number of double bonds which causes the fish oil to be susceptible to oxidation. The shelf lives of fish oil enriched products are thus limited by fast oxidation rates of the fish oil which causes development of off flavours as well as degeneration of the beneficial health effects of the fish oil. At the present moment this is a barrier for their access to the market and it is necessary to develop techniques to protect the oil against oxidation. Emulsification of the oil has been put forward as a strategy for protection against oxidation, but whether that is beneficial seems to depend on the food matrix to which the oil is added [1,2]; see figure 1. It is thus interesting to investigate the pure emulsions to gain knowledge about the oxidation without the effects of an external food matrix. It has been seen that some factors that influence the oxidation in pure emulsions are the type of emulsifier, the oil droplet size and the pH [3]. This dependence has led to the belief that the oxidation is initiated at the interface between oil and water and that the thickness or composition of the interface can be controlled to ensure optimum stability of the emulsions.