Recent progress in food-grade double emulsions: Fabrication, stability, applications, and future trends

Compared with ordinary emulsions, the unique structures endow double emulsions with special functions, which makes them have broad prospects in delivering biologically active substances and replacing fats. In recent years, due to the instability of double emulsions, numerous experiments have been carried out on their preparation technology as well as stabilization methods. This review emphatically summarizes the research progress of double emulsions, including preparation techniques, factors affecting stability, stabilization mechanisms, and related applications. At present, in addition to the traditional mechanical agitation and ultrasonic emulsification, membrane emulsification, phase inversion, and microfluidic emulsification are the main research directions, all of which can improve the stability. Moreover, the stabilizer is also a crucial factor affecting the stability of the double emulsion. Hence, in this article emphasis is placed on surfactants, biopolymers, and solid particles. The applications of double emulsions in food industry can be divided into the following categories: encapsulating substances, controlling the release, and being served as fat substitutes. Furthermore, in the future, the main challenges are to commercialize the double emulsions and enhance their safety in food applications. Additionally, developing high internal phase Pickering double emulsions and O/W/O double emulsions may become the major research trends.