A review on food-grade-polymer-based O/W emulsion gels: Stabilization mechanism and 3D printing application

Food-grade polymers such as proteins and polysaccharides have attracted great interest in recent years as excellent stabilisers for emulsion gels due to their good biocompatibility, environmental friendliness, and low cost. The obtained emulsion gels with specific properties can be used as extrudable inks in 3D printing. To further understand the application of food-grade polymers in emulsion gels construction, the interaction between proteins and polysaccharides as well as their mechanisms of stabilizing emulsion gels were reviewed. Besides, the feasibility of applying emulsion gels to 3D printing systems is discussed. Finally, this paper provides a brief outlook on using 3D-printed emulsion gels as practical foods. Proteins after the physical, chemical, and enzyme modifications are allowed to obtain emulsion gels by emulsion filling and particle aggregation. The mechanism of polysaccharide-based emulsion gels construction can be mainly distinguished as single stabilizing, bulk gelling, polysaccharide complexion stabilizing and dual-layer stabilizing, respectively. When used together, proteins and polysaccharides mainly stabilize emulsion gels by polysaccharide thickening, multilayer wrapping, or complex stabilizing. The emulsion gels with properties of shear-thinning, smooth flowability, and powerful stability can be successfully used as 3D printing inks. This review gathers and analyses mechanisms of applying food-grade polymers like proteins and polysaccharides to stabilize emulsion gels and summarizes the feasibility of emulsion gel application for 3D printing. This work can provide basic guidance for the development and application of low-fat and healthy fat-substitutes.