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

The thermogelation properties of canola protein isolate (CPI) in a mixed system with kappa-carrageenan (kappa-CAR) were examined using dynamic rheological testing. The effects of pH, NaCl, kappa-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-kappa-CAR gels with maximized G' values (greater than or equal to 44 000 Pa) and minimized tan delta values (0.01-0.11). It was found that canola protein-carrageenan gel formation was strongly pH-, NaCl- and kappa-CAR concentration-dependent. Results indicated that the optimum conditions for CPI-kappa-CAR gels was pH 6, 0.05 M NaCl, 3% kappa-CAR and 15% CPI. Samples prepared at pH 6 showed high G' (95 465 Pa) and low tan delta(0.15) values. High G' values indicate stronger intermolecular network and increased interactions between protein-protein and protein-polysaccharide molecules, while low tan delta values indicate a more elastic network. A synergistic behavior between CPI and kappa-CAR was observed with superior network strength (high G' values) for the mixed gels at temperatures above 80 degreesC. Further, the gels showed improved network structure (low tan delta values) during the heating and cooling phases. The canola protein-kappa-carrageenan mixtures exhibited very strong and elastic networks, indicating that CPI can serve as a structuring agent in mixed food systems. (C) 2004 Elsevier Ltd. All rights reserved.