Adsorption and rheological properties of biopolyrners at the air-water interface

Dynamics of adsorption and viscoelasticity of biopolymers (beta-lactoglobulin (beta-lg) + polysaccharides (PS)) at 20 degrees C and pH 7 have been studied. Protein concentration in the bulk phase was 0.1 wt %, and the concentration of polysaccharides (xanthan gum, A-carrageenan, and propylenglicol alginate with different degrees of esterification and viscosity) was varied from 0.1% to 0.5 wt %. The results reveal a significant effect of surface-active and non surface-active polysaccharides on the dynamics of the formation and viscoelasticity of adsorbed films at the air-water interface. The rate of diffusion of the biopolymers increased in the mixed systems, but the effect was more significant at the highest concentration of polysaccharide (0.5 wt %). The rate of rearrangement of the adsorbed films decreased in the presence of polysaccharides as compared to the protein film. Competitive adsorption, complexation and limited thermodynamic incompatibility between P-lactoglobulin and polysaccharide would explain the observed effects. (c) 2006 American Institute of Chemical Engineers.