The effects of xanthan conformation and sucrose concentration on the rheological properties of acidified sodium caseinate-xanthan gels

Xanthan solution transitions caused by annealing at different temperatures were studied by oscillatory rheology. The rheological behaviour of solutions evaluated at 10 degreesC showed different irreversible xanthan transitions, depending on the annealing temperature. The effect of xanthan conformation and casemate, xanthan and sucrose concentrations on the mechanical and stress relaxation properties of acidified dairy gels were also investigated. Xanthan transitions produced different structural characteristics in mixed gels, as observed by their relaxation time and residual stress. The amount of sucrose played an important role in the network formation of gels and on the final elasticity. Intermediate concentrations of sucrose yielded gels that were finer than those obtained with low sucrose content, whereas at high amounts of this co-solute, the gels became more fragile. This quadratic effect of sucrose occurred at lower sucrose contents than in protein-sucrose or polysaccharide-sucrose systems. The mechanical properties at equilibrium were affected only by the strength of the interactions between caseinate and xanthan. (C) 2004 Published by Elsevier Ltd.