Ultra structure of oil-in-water emulsions

摘要: Addition of fish oil to industrially prepared food products is attractive to the food industry because of the well-documented health effects of long chain polyunsaturated omega-3 fatty acids in the fish oil. However, omega-3 fatty acids are highly susceptible to lipid oxidation because of their many double bonds, and the incorporation of fish oil into food products is therefore limited by the development of unpleasant off-flavours. It has been shown that addition of fish oil to selected food products as emulsions rather than crude oil changes the products’ stability against oxidation but whether emulsification is an advantage or not seems to depend on the food matrix to which the emulsion is added (1, 2). Hence, we sought to determine the factors which controls the oxidation in pure emulsions. A schematic overview of an emulsion is shown in figure 1. It has been proposed that oxidation of oil-in-water emulsions is initiated at the interface between oil and water and that the oxidation is to some extent dependent on the micro structure of the emulsion; including the size of oil droplets, the emulsifier type and the thickness of the interface. Also the distribution of the emulsifier in the water phase might affect the oxidation since some emulsifiers have antioxidant properties, eg sodium caseinate is a metal chelator which can sequester transition metals that would otherwise act as prooxidants. The potential link between the oxidative stability and the interface structure is not well understood. The main objective of this study is to characterize the structure of fish oil emulsions with respect to oil droplet size, distribution, and ultimately to view the structure and thickness of …