Rheological characteristics of commercial canola protein isolate–κ-carrageenan systems

The thermogelation properties of canola protein isolate (CPI) in a mixed system with κ-carrageenan (κ-CAR) were examined using dynamic rheological testing. The effects of pH, NaCl, κ-CAR and protein concentrations on the gelling ability of CPI were evaluated. Factorial and response surface optimization models were used to identify the processing conditions that would result in CPI–κ-CAR gels with maximized G′ values (≥44 000 Pa) and minimized View the MathML source values (0.01–0.11). It was found that canola protein–carrageenan gel formation was strongly pH-, NaCl- and κ-CAR concentration-dependent. Results indicated that the optimum conditions for CPI–κ-CAR gels was pH 6, 0.05 M NaCl, 3% κ-CAR and 15% CPI. Samples prepared at pH 6 showed high G′ (95 465 Pa) and low View the MathML source values. High G′ values indicate stronger intermolecular network and increased interactions between protein–protein and protein–polysaccharide molecules, while low View the MathML source values indicate a more elastic network. A synergistic behavior between CPI and κ-CAR was observed with superior network strength (high G′ values) for the mixed gels at temperatures above 80 °C. Further, the gels showed improved network structure (low View the MathML source values) during the heating and cooling phases. The canola protein–κ-carrageenan mixtures exhibited very strong and elastic networks, indicating that CPI can serve as a structuring agent in mixed food systems.