Construction and formation mechanism of phase-change polysaccharide–protein composite emulsion gels: For simultaneous printing of food products with complex structures and fine patterns

With the development of the intelligent direction of food 3D printing, people have a strong aesthetic interest in food printing prototypes. In order to investigate the ability of food-based materials to print complex structures and fine patterns simultaneously, three phase-change hydrocolloids with different mechanical strengths after cooling were selected: xanthan gums (Xg), low acyl gellan gums (Gg), and starches (Ss) with ovalbumin to form Xg-ovalbumin emulsion gel (Xg-OEG), Gg-ovalbumin emulsion gel (Gg-OEG), and Ss-ovalbumin emulsion gel (Ss-OEG), respectively. Ss-OEG printed fine patterns with a minimum size of 1.5 mm accurately at a Ss concentration of 1.5%, and was able to print suspended structures, had continuous filament strips and tight layer-to-layer stacking, with the ability to print complex structures and fine patterns simultaneously. Compared with Xg-OEG and Gg-OEG, Ss-OEG had high viscoelasticity and mechanical strength, suitable fluidity, small size of oil droplets without aggregation, dense network structure, and high surface hydrophobicity and amide A peak intensity and the low free sulfhydryl content. Thus, Ss endowed OEG with a certain viscoelasticity and mechanical strength, and caused massive aggregation of proteins through forming disulfide bonds, hydrophobic interactions, and hydrogen bonds. Aggregated ovalbumin and Ss formed a stable and strong network structure, emulsified oil droplets filled in the network, the three tightly crosslinked together to form an emulsion gel with excellent printing ability. This research offered the possibility of simultaneously printing complex structures, high-resolution patterns using food-based materials, also providing a theoretical basis for the design of complex and fine printed products.