Upon further heating of mixed solutions, the storage modulus did not change until the denaturation temperature of WPI was reached. This finding is in agreement with de la Fuente, Hemar, and Singh (2004) who reported that thermal denaturation of WPI is unaffected by the presence of κ-carrageenan. However, subsequent aggregation and gelation behavior of denatured protein were strongly affected depending on the κ-carrageenan concentration. In the case of stranded WPI gels (50 and 100 mM NaCl), with the addition of κ-carrageenan at 0.2 and 0.4%, the storage modulus nearly doubled during the ascending temperature ramp (above gelation temperature) and holding at 80 °C (Fig. 2a, b). It is very likely that the presence of κ-carrageenan enhanced the aggregation of denatured proteins during the heating process. Croguennoc et al. (2001) explained the possible mechanism by depletion of carrageenan polymers from the surfaces of neighboring protein aggregates. Once the protein aggregates reach a critical size, they experience an induced depletion attraction due to an unbalanced osmotic pressure rising from the exclusion of polysaccharide (Tuinier et al., 2000). This favors the association of large aggregates and accelerates their growth resulting in increased local concentration. These findings are in agreement with the observations of Capron, Nicolai, and Durand (1999), who showed that κ-carrageenan increases the aggregation of β-lactoglobulin (2% w/w in 100 mM NaCl at pH 7.0) into large fractal particles. This means the phase separation mainly occurs before the gel point, but only at elevated temperatures where sufficient aggregation of whey proteins is obtained to reach a critical size. At these temperatures, κ-carrageenan does not contribute directly to the gel network because it is found in the form of random coils. However, the phase separation between the dispersed κ-carrageenan and large aggregates increased the local concentration of whey protein in the continuous phase. This explains the higher storage modulus of the mixed gels at low κ-carrageenan concentrations compared to that of the protein alone. The physico-chemical properties of dispersed systems are determined in part by their continuous phase and the modulus of a gel is proportional to the square of hydrocolloid concentration (Tolstoguzov, 1995). Thus, an increase in the protein concentration of the continuous phase would contribute to the mechanical properties of mixed gels. The increase in gel firmness with low concentrations of polysaccharide has been previously reported for other polysaccharides such as guar gum (Fitzsimons, Mulvihill, & Morris, 2008), xanthan (Bryant & McClements, 2000), pectin (Beaulieu et al., 2001), cassia gum (Gonçalves, Torres, Andrade, Azero, & Lefebvre, 2004) and locust bean gum (Tavares & Lopes da Silva, 2003).