Gellan Gum Modification and Structural Regulation for Food Applications: Delivery Systems and Digestive Behavior

Gellan gum (GG) is an anionic microbial polysaccharide widely used in foods because of its efficient gelation, thermal stability, and ion-responsive structuring. However, the contrasting limitations of high- and low-acyl GG, together with their sensitivity to molecular weight, ions, pH, thermal history, and food-matrix composition, restrict their performance in complex products. This review distinguishes four intervention levels of GG modification and structural regulation: covalent modification, chain-architecture regulation, supramolecular regulation, and food-matrix composite structuring. These modifications and structural regulations alter chain properties, helix association, junction-zone formation, interfacial organization, and phase connectivity, thereby affecting gelation, texture, water retention, emulsion stability, processability, and release behavior. Food applications are evaluated through their structure–function relationships across diverse food systems. Particular attention is given to gastrointestinal disassembly, nutrient digestion, bioactive release, and colonic fermentation. Current evidence strongly supports the role of GG structural regulation in food texture and physical stability, whereas evidence for digestive modulation and physiological effects remains limited and is largely based on formulation-specific in vitro studies. Overall, this review provides a structure-guided framework for application-specific selection of GG intervention strategies.