Sodium alginate and casein were used to prepare composite emulsion gels, and the effects of different preparation methods and sodium alginate concentrations on the structure of emulsion gels were studied using rheology and electron microscopy. The formation mechanism of sodium alginate-casein composite emulsion gel was discussed. The results showed that, at the casein concentration of 80 g/L, the gel structure gradually transformed from casein-dominated single network to "water in water" emulsion structure with the increasing of alginate concentration. Casein was acted as the continuous phase and sodium alginate was acted as the dispersed phase in the above system. When the concentration of sodium alginate increased to 7.5 g/L, bicontinuous structure was observed. After incorporating oil droplets, the composite emulsion gels still exhibited similar structural transformation, and the oil droplets always located in the casein-dominated phase despite of the preparation difference of the emulsion gels. By comparison, the effects of the two preparation methods on the structural characteristics of emulsion gels were limited, but method 1 was simpler, and the emulsion gel prepared by it showed a smaller particle size. The formed composite emulsion gels displayed better texture when the concentration of sodium alginate was at 4 g/L. Our results provide theoretical basis and technical reference for the development of new gel foods.

emulsion; gel; sodium alginate; casein; gelation