Improving gelling properties of fish gelatin by γ-polyglutamic acid with four different molecular weights

This work investigated gelling properties and structural characteristics of fish gelatin (FG) modified by four different molecular weights of gamma-polyglutamic acid (gamma-PGA) with 700, 1000, 2000 and 3000 kDa, respectively. Gelation-melting transition temperature and gel strength increased with the increase of molecular weight in gamma-PGA. Especially, gamma-PGA in 3000 kDa made gel strength, gelation and melting temperatures reaching to 628.08 g (P < 0.05), 22.30 degrees C and 30.17 degrees C (P < 0.05), respectively. Non-covalent interactions existed in FG and gamma-PGA. Such as, new hydrogen bonds were generated between them. Moreover, gamma-PGA with increased molecular weight enhanced three-stranded helical structure and microscopic meshwork of FG. Finally, a schematic model was described to illustrate the interaction between FG and gamma-PGA in different molecular weights. On the whole, gamma-PGA with high molecular weight significantly improved gelling properties of FG, and could be a potential modifier of FG in the future.