11-2 |
Surface and gelation properties of commercial canola protein isolate - carrageenan systems |
F. O. URUAKPA and S. D. Arntfield. Dept. of Food Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada Utilization of oilseed proteins in food systems is based on the ability of the proteins to provide some functional properties to the food product. Such functions include the ability to contribute to structure formation or to promote associations between food components. It is hypothesized that the inclusion of hydrocolloids such as carrageenan, in a mixed system with canola protein isolate, will promote network formation. In this study the impact of pH, NaCl concentration, carrageenan and protein concentrations on the gelation and surface properties of canola protein was evaluated. The protein surface property was characterized by the surface hydrophobicity (So) determined using 8-anilino-1-naphthalenesulphonate (ANS) as a fluorescent probe. The rheological properties of heat-induced gels were characterized by small deformation testing using a Bholin dynamic rheometer. Both pH and carrageenan concentration significantly (P<0.05) affected So; high So values resulted at pH 6-8 and low carrageenan concentration. High So values are indicative of increased exposure of hydrophobic amino acid residues due to changes in protein structure. Rheological properties of heat-induced gels prepared from these mixed systems were also affected by pH and carrageenan concentration. Samples prepared at pH 6-8 had high G¢ (storage modulus) values, indicative of stronger gel structure and increased interactions between proteins. Lower tan delta values (tan d=G²/G¢), as were obtained at higher pH (pH 9-10) and low carrageenan concentrations, are indicative of very good gel structure. The rheological properties of heat-induced gels containing canola protein isolate suggest that canola protein can serve as a structuring agent in foods of mixed composition. While the So values were not directly related to the gel characteristics, the exposure of hydrophobic amino acid residues in canola protein under some conditions could make these systems suitable for stabilizing protein-lipid association, as can be found in food emulsions.
Session 11, Food Chemistry: Proteins
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