Competitive adsorption between surface-active polysaccharides and proteins: surface pressure and film rheology behavior

PÉREZ, OSCAR E; MARTÍNEZ, KARINA D; MARINEZ, MARÍA JULIA; CARRERA-SÁNCHEZ, CECILIO; PIZONES-RUÍZ HENESTROSA, VÍCTOR; RODRÍGUEZ-PATINO, JUAN M; PILOSOF, ANA MR.

Le Mans, Francia

Congreso; Food Colloids 2008, Polymeres, Colloids and Interfaces; 2004

Universite du Maine

The interactions between proteins and polysaccharides at the air-water interface are of great importance for the formation and stability of food colloids as well as for the design of interfacial films with specific properties. One distinctly group of surface-active polysaccharides are the esters of alginic acid, propylene glycol alginate (PGA). Hidroxypropylmethylcellulose (HPMC) is a cellulose derivative which has methyl and hydroxypropyl groups added to the anhydroglucose backbone. HPMC is of special interest for controlled-release matrices.  Methyl substitutes constitute hydrophobic zones along the cellulose backbone whereas hydroxypropyl groups are more hydrophilic. The introduction of these hydrophobic groups allows HPMC to behave as a surfactant. Due to their surface-active character, competitive adsorption could occur in mixtures of these polysaccharides and proteins. In this work we review the interfacial behavior of the following mixed protein + polysaccharide systems: β-lactoglobulin (βlg) + PGA, caseinomacropeptide (CMP) + PGA, whey protein concentrate (80% protein)(WPC) + HPMC, soy protein isolate (SP) + HPMC in order to understand how the surface active characteristics of each component and their film forming abilities impact the properties of the mixed films. Time-dependent surface pressure and surface dilatational properties of single and mixed systems at protein or polysaccharide bulk concentrations that allows monolayer saturation were determined in an automatic drop tensiometer IT Concept at 20°C and pH 7. At this pH the electrostatic complexation between proteins and polysaccharides is mainly prevented. The surface pressure over time for HPMC mixtures with WPC or SP, showed a competitive behavior, dominated by HPMC because of its unusual strong surface-activity. The surface dilatational modulus (Ed) of mixed films at short adsorption times was dominated by the component that adsorbed more rapidly. At long adsorption times, film rheology was dominated by the component with the strongest Ed or lowest phase angle, WPC in the mixture WPC + HPMC and HPMC in the mixture SP + HPMC. The surface pressure over time for mixtures of a weak surface-active polysaccharide as PGA with proteins (βlg or CMP) was dominated by βlg but showed an intermediate value between single components for CMP, in spite of being CMP much more surface-active than βlg.  blg also determined the rheological properties of the mixed film because  it formed films with much better surface dilatational properties than PGA. In the case of CMP + PGA mixture, where both components had similar Ed, it was  observed that the relative viscoelasticity of the mixed film was lower than that of single components indicating an antagonic effect. It can be concluded that during competitive adsorption between polysaccharides and proteins at high bulk concentrations, the surface pressure would be dominated by the component that exhibits the highest surface activity if this component also forms films with a high surface dilatational modulus. The film rheology would be mainly dominated by the biopolymer that can form the strongest viscoelastic films, but antagonic interactions at the surface may alter this behavior.