3D/4D Printing of Polysaccharide–Protein Composite Food Gels: Molecular Interactions, Structural Regulation, and Applications in Food Quality Enhancement

Polysaccharide–protein composite food gels, owing to their high structural tunability, favorable printability, and nutritional functionality, have emerged as an important material platform for 3D/4D food printing. However, existing reviews have largely focused on material preparation or printing technologies, with limited analysis of polysaccharide–protein synergism and the quantitative links between molecular interactions, rheology, printability, and functionality. This review uses VOSviewer to analyze co-occurrence patterns in the literature on gels and food printing over the past decade. It examines how molecular interactions and crosslinking regulate gel networks and rheology, and how formulation, printing parameters, and post-processing affect texture, water-holding capacity, printing fidelity, and structural stability. Printability is evaluated through yield stress, shear-thinning, thixotropic recovery, and G′/G″, alongside a comparison of six printing technologies. Recent advances in 4D-printed deformable gels responsive to temperature, humidity, pH, and microwave stimulation are further summarized, with particular emphasis on their potential applications in smart foods, dysphagia-oriented diets, and functional delivery systems. Finally, current research trends are discussed, highlighting a shift from empirical formulation optimization toward multiscale structural regulation, elucidation of dynamic response mechanisms, and health-oriented personalized food design. This review provides a conceptual and practical framework for advancing both the fundamental understanding and industrial application of polysaccharide–protein composite gels in food printing.