Textural properties of a model aqueous phase in low fat products.: Part 1:: Alginate, caseinate and starch in isolation, and in starch containing binary mixtures

The effect of increasing additions of calcium on the textural properties of alginate, caseinate and starch dispersions was investigated to provide a baseline for further work on mixtures of these biopolymers. Increasing concentrations of calcium transformed the alginate solutions into gels having a maximum rigidity at 1000 and 300 p.p.m. Ca2+ for 2.0 and 0.5% of the polysaccharide, respectively. Gelation was achieved by cooling which unveiled a two stage process of network formation. Caseinate solutions (12%) showed an increased viscosity with a rising Ca2+ concentration up to 2250 p.p.m., above which viscosity decreased. Starch (2.5%) exhibited a slight loss in storage modulus (G') with increasing levels of calcium. The texture of the alginate starch mixture was determined by the alginate component (two stage gelation process), but inverted to that of starch at high levels of added Ca2+. In the absence of the counterion, casein had an adverse effect on the strength and cohesion of starch networks. At 400 p.p.m. Ca2+, the protein forms a continuous liquid like phase which suspends the starch inclusions thus dictating the textural properties of the mixture. Caseinate continues to dominate up to 1200 p.p.m. Ca2+ at which point the starchy matrix influences the system once more. Finally at higher levels of the counterion the sample phase inverts back to a starch continuous gel. Part 2 of this work examines the effect of calcium on the remaining preparations in order to facilitate the formulation of improved low fat products.