Impact of hydroxypropylmethylcellulose on whey protein concentrate spread film at the air-water interface: Structural and surface dilatational characteristics

Abstract

The static (film structure and elasticity) and dynamic features (surface dilatational properties) of whey protein concentrate (WPC) spread films at the air-water interface, as influenced by three commercial hidroxypropylmethycelluloses (HPMC), i.e., E4M, E50LV and F4M, were studied, at 20. °C, pH 7 and I=. 0.05. M. To this end a fully automated Wilhelmy-type film balance was used. The results showed a significant influence exerted by HPMC surface active polysaccharides on the WPC film structure. After the polysaccharide addition in the aqueous subphase the π-through area isotherms changed, especially for the highest molecular weight HPMC, as the time increased. Moreover, the presence of HPMC also decreases the surface modulus and the relative viscoelasticity of the WPC protein films. These results can be interpreted in terms of the ability of the polysaccharides to absorb at the air-water interface by itself, penetrate into the spread protein film due to its surface activity and increasing surface pressure. The existence of limited thermodynamic compatibility between the protein and HPMC, occurring in the aqueous phase and at the air-water interface, could be the cause of the observed phenomena, which in turn would be determined by the molecular properties of the cellulose derivative. As mixtures of proteins and polysaccharides are often used in many technological applications, the results presented here should help to improve the processes involved in the formation and stabilization of complex colloidal formulations like foams and emulsion based on these biopolymers.