Interactions of κ-carrageenan with whey proteins in gels formed at different pH

Abstract

The objective of this study was to investigate the influence of κ-carrageenan on textural properties of whey protein isolate gels formed by heating at 80 °C for 30 min in the pH range from 1–12. In the absence of polysaccharide, very strong and elastic gels were obtained using 10% WPI at pH 7–8. In the presence of κ-carrageenan, the highest shear stress value was observed at pH 6, but strong gels were obtained over a broad pH range up to 11. WPI at a concentration of 3% did not form a self-supporting gel, but significantly enhanced the shear stress values of 0.5% κ-carrageenan, particularly at pH 6–7. A similar enhancing effect of 3% unheated milk protein on gk-carrageenan gels at pH 6.7 was also observed. At pH 6–7, where optimal gelation of mixtures was observed, the presence of κ-carra-geenan resulted in smaller increases in protein surface hydrophobicity after heating, as determined by the fluorescence probe 1-anilinonaphthalene-8-sulfonate. Under these conditions, small angle X-ray scattering studies indicated the formation of a mixed structure gel with attractive interparticle interactions.