Roles of additional emulsifiers in the structures of emulsion gels and stability of vitamin E

The role of the oil droplets in emulsion gelation (as active or inactive fillers) was modified by additional emulsifiers, and structures and functionalities of emulsion gels were evaluated. Emulsion gels based on denatured protein (whey protein isolate) were prepared via an acid-induced approach, and four emulsifiers, including glycerol monostearate (MG), tween 20 (TW), modified starch (OSA) and gum Arabic (GA) were tested. The including of MG or TW led to delayed onset of gelation, and the emulsion gels formed were of lower gel strength (described as storage modulus and fracture force), compared with the emulsion gels without additional emulsifiers. Increase in the content of MG or TW resulted in the gels with lower water holding capacity, and slight changes in swelling ratio. The presence of OSA or GA allowed faster gelation of the emulsions, forming gels with higher storage modulus and fracture force. Increase in the content of OSA or GA did not affect WHC of the gels, but contributed to higher swelling ratios. Microstructural observation indicated that the emulsion gels with OSA or GA had smaller pore size. When vitamin E was incorporated within the gels, the emulsifiers presented different effects on its degradation kinetics. Vitamin E degraded much faster in the systems with higher content of MG or TW, and lower retention ratios were obtained after the storage (55 °C for 12 days). On the contrary, the emulsion gels with OSA or GA provided good protection for vitamin E, and increase in the content of the emulsifiers allowed higher retention ratios.