Rheological behavior, emulsifying properties and structural characterization of phosphorylated fish gelatin

Rheological, microstructural and emulsifying properties of fish gelatin phosphorylated using sodium trimetaphosphate (STMP) were studied. Phosphorylation was carried out at 50 degrees C for 0, 0.5, 1 or 2 h. Rheological behaviors indicated that phosphorylation decreased gelation rate constant (k(gel)) and apparent viscosity of gelatin solutions. Phosphorylation time was inversely proportional to tan delta; gelling and melting points of fish gelatin gels; however gel properties could be improved by short time of phosphorylation. Scanning electron microscopy and atomic force microscopy revealed that longer time of phosphorylation resulted in looser gel network with more aggregation. Longer phosphorylation time could stabilize fish gelatin emulsions, and endowed emulsions with smaller particle size and lower coefficient viscosity, but higher zeta-potential values. These results suggested that phosphorylation could be applied to obtain fish gelatin with varying functional properties suitable for numerous industrial applications.