The rheological properties of gelatin gels containing κ-carrageenan. The role of polysaccharide

The influence of an anionic polysaccharide, κ-carrageenan, on the rheological properties of low-concentration (1.0 wt %) gelatin gels has been studied in a wide range of low polysaccharide concentrations (1 × 10−3–5 × 10−1 wt %) at a temperature of 14.0°C and pH values slightly higher than the isoelectric point of gelatin. The parameters characterizing the rheological properties of the gels are governed by the mass ratio between the polysaccharide and gelatin, which are able to form (bio)polyelectrolyte complexes in aqueous systems. There is a critical κ-carrageenan-to-gelatin mass ratio Z ≅ 0.1, above which the yield stress of the gels and their effective viscosit at stresses exceeding the yield point drastically rise. The increase in these rheological parameters correlates with a growth in the particle size of κ-carrageenan-gelatin polyelectrolyte complexes, which are formed in the aqueous bulk phase at an elevated temperature and precede gelation.