Dynamics of adsorption of whey proteins and hydroxypropylmethylcellulose mixtures at the air-water interface

PÉREZ, OSCAR E; CARRERA-SÁNCHEZ, CECILIO; RODRÍGUEZ-PATINO, JUAN M; PILOSOF, ANA MR.

Le Mans, Francia

Congreso; Food Colloids 2008. Polymeres, Colloids and Interfaces; 2008

Universite du Maine

The formation and stability of foams and emulsions is a key quality parameter in a wide range of applications in food science, since consumer perception of quality is strongly influenced by appearance. Thus, foam and emulsion functionality results highly influenced by the surface and interfacial properties of the surface-active components, i.e. proteins, polysaccharides and surfactants, present in the system and their interactions. One type of these interactions is the competition between different surface-active biopolymers, which should have a strong impact on the functionality of foams and emulsions. Whey protein concentrates (WPC) and isolates (WPI) are important food ingredients because of their desirable functional properties, such as gelation, foaming and emulsification. On the other hand, most high-molecular-weight polysaccharides, being hydrophilic, do not have much of tendency to adsorb at the air-water interface. Although, one distinctly group of surface-active polysaccharides are cellulose derivatives, which possess very interesting physico-chemical properties and also many technological applications and, among them, hydroxypropylmethylcellulose (HPMC). The aim of this research is to quantify (by measurements of adsorption kinetics) the competitive adsoption between WPC proteins and HPMC, as they are often used together in many food applications, and the results of potential effects of competition are unknown. The adsorption kinetics of WPC proteins and three different HPMC (so called E4M, E50LV and F4M) mixed systems were determined. The concentration of both, protein and HPMC, and the WPC/HPMC ratio in the aqueous bulk phase were variables, while pH (7), ionic strength (0.05M) and temperature (20ºC) were kept constant. The differences observed between mixed systems were according to the relative bulk concentration of biopolymers and molecular structure of HPMC. At short adsorption times, the results show that: -         Under conditions where both WPC and HPMC could saturate the air-water interface by their own or when CHPMC³ CWPC, the polysaccharide dominates the surface. -         At such concentrations where none of the biopolymers was able to saturate the interface, a synergistic behaviour was observed for celluloses with lower surface activity (E50LV and F4M), while a competitive adsorption was observed for E4M (HPMC with the highest surface activity). At long-term adsorption the rate of penetration controls the adsorption of mixed components. In general, the values of rate constant of adsortion/penetration were lower than those of pure components. These results reflect the competitive adsorption between the biopolymers for the interface (especially in the presence of E4M) or the higher resistence to penetrate in the formed film, at short adsoption time, when exists a “depletion mechanism”. Finally, the order in which the different components get the interface will influence the final equilibrium surface composition.