The effect of casein on the viscosity of solutions of hydrocolloids

The apparent viscosities of aqueous solutions of guar gum, locust bean gum, sodium carboxymethylcellulose and k‐carrageenan have been measured over a range of shear rates from 14 to 1142 s−1. Comparable measurements were made on solutions to which different quantities of casein (10‐40 g litre−1) had been added. For all the solutions a power law equation describes the variation of relative viscosity with shear rate. Addition of casein has no effect on the solutions of guar and locust bean gum, but does affect the rheology of solutions of sodium carboxymethylcellulose and k‐carrageenan. The behaviour of k‐carrageenan indicates a dependence on the polyanion:casein ratio, reaching a maximum at a concentration ratio of 1:4. The only significant solute‐solute interactions in the hydrocolloid‐casein solutions are electrostatic in nature.