Phosphate structure-dependent modification tailors gelation and interfacial properties of fish gelatin

TSPP, STPP, and STMP induced distinct molecular rearrangement pathways. • TSPP reinforced gel networks through enhanced molecular organization. • STPP promoted stable interfaces and improved emulsion stability. • STMP enhanced emulsifying activity via rapid interfacial adsorption. Fish gelatin (FG) is a promising functional biopolymer, but its application in structured food systems is restricted by insufficient gel strength, thermal stability, and interfacial stabilization ability. Although phosphorylation has been widely applied to improve protein functionality, how phosphate structures regulate molecular rearrangement and determine different functional outcomes remains unclear. This study investigated the structure-dependent effects of three phosphate reagents, sodium pyrophosphate (TSPP), sodium tripolyphosphate (STPP), and sodium trimetaphosphate (STMP), on the multiscale structure and functionality of FG. All phosphate treatments successfully introduced phosphorus-containing groups into FG while largely preserving gelatin chain integrity; however, the extent and pattern of molecular restructuring varied among phosphate reagents. TSPP treatment resulted in the highest phosphorus content and was associated with the most pronounced conformational rearrangement, as evidenced by increased ordered secondary structures, altered tertiary microenvironments, enhanced surface hydrophobicity, and formation of a denser gel network with improved mechanical properties. In contrast, functional enhancement was not directly proportional to phosphorus content. STPP generated a more balanced structural state, resulting in improved thermal stability and superior emulsion stabilization, whereas STMP mainly enhanced interfacial adsorption ability but provided limited improvement in long-term emulsion stability. These results reveal that phosphate structure plays a critical role in regulating the structural evolution and functional direction of modified FG, whereas phosphorus content alone cannot fully predict functional performance. Download: Download high-res image (524KB) Download: Download full-size image