Microbial transglutaminase (MTGase) modified fish gelatin-γ-polyglutamic acid (γ-PGA): Rheological behavior, gelling properties, and structure

•γ-PGA combined with MTGase made a better texture of fish gelatin (FG).•MTGase promoted FG and γ-PGA crosslinks.•MTGase can increase the viscosity of FG-γ-PGA system.•A schematic model was proposed to illustrate the progressive modification. Fish gelatin (FG) has been extensively studied as a potential substitute for mammal gelatin. However, FG often requires different modification methods to change its physical and chemical properties due to its low gelling properties. Here, γ-polyglutamic acid (γ-PGA) and microbial transglutaminase (MTGase) were combined to modify FG to improve its gelling properties. The γ-PGA at 0.04% (w/v) and MTGase of different concentrations (0.02–0.08%, w/v) were used to modify FG, and the effects of complex modification on the gelling properties and structure of FG were studied. When the MTGase content was 0.08% (w/v), FG had the best gelling properties. In addition, the complex modification of MTGase and γ-PGA hindered the formation of the triple helix during the FG gel process. This reduced the gel rate, but significantly increased its viscosity. A schematic model was also proposed to illustrate the complex modifications of FG by MTGase and γ-PGA.