Polyelectrolyte Polysaccharide-Gelatin Complexes: Rheology and Structure

General features of rheological properties and structural peculiarities of polyelectrolyte polysaccharide-gelatin complexes were discussed in this paper. Experimental results were obtained for typical complexes, such as kappa-carrageenan-gelatin, chitosan-gelatin and sodium alginate-gelatin complexes. A rheological method allows us to examine the physical state of a complex in aqueous phase and the kinetics of the sol-gel transition and temperature dependences of properties as a result of structural changes. The storage modulus below the gelation temperature is constant, which is a reflection of the solid-like state of a material. The gels of these complexes are usually viscoplastic media. The quantitative values of the rheological parameters depend on the ratio of the components in the complexes. The formation of the structure as a result of strong interactions of the components in the complexes was confirmed by UV and FTIR data and SEM analysis. Interaction with polysaccharides causes a change in the secondary structure of gelatin, i.e., the content of triple helices in an alpha-chain increases. The joint analysis of the structural and rheological characteristics suggests that the formation of additional junctions in the complex gel network results in increases in elasticity and hardening compared with those of the native gelatin.