RHEOLOGICAL PROPERTIES OF PROTEIN/STARCH MIXED GELS

The influence on the viscoelastic behaviour of the heat transition temperatures of starch and protein in gelatinous systems prepared from the two components was studied. Four different starches were combined with Bovine Serum Albumin (BSA) in several protein-to-starch ratios. Both the transition temperature and the rates of gelation of the components were critical for the behaviour of the complex systems. In those cases where the starch gel was formed before the protein gel, the storage and loss moduli of the complex system could be predicted by a simple addition of the moduli of the components at corresponding concentrations. When the gelation occurred in the reverse order, the gels were considerably stronger than predicted by the additivity model. When the starches were combined with gelatin, the complex gels were all weaker than predicted. The gelation of gelatin was very slow compared to that of the starches and the BSA, and it is likely that the weakness of these gels was due to the aggregation of the amylose molecules or some other part of the starch retrogradation process.