SOY PROTEIN- POLYSACCHARIDES INTERACTIONS AT THE AIR-WATER INTERFACE

MARTINEZ, KARINA D.; CARRERA SANCHEZ CECILIO; PIZONES RUIZ-HENESTROSA, VICTOR; RODRÍGUEZ PATINO, JUAN M.; PILOSOF, ANA M.R.

FOOD HYDROCOLLOIDS

Elsevier

Lugar: Harrogate; Año: 2007 vol. 21 p. 804 - 812

0268-005X

This work studies the interfacial behaviour of mixed soy protein (SP) + polysaccharide (PS) systems to gain knowledge on the interactions between these biopolymers at the air-water interface under dynamic conditions at neutral pH where a limited incompatibility between  macromolecules can occur. The polysaccharides used were: hydroxypropylmethylcellulose (HPMC) as surface active polysaccharide; lambda carrageenan (lC) and locust bean gum (LB) as  non-surface active polysaccharides. Protein and polysaccharide concentration in the mixed systems were 2% and 0.25% respectively. The dynamic surface pressure and rheological properties of films were evaluated with a drop tensiometer at 20ºC, pH 7 and ionic strength 0.05M. The presence of HPMC and lC greatly increased the surface pressure, surface dilatational elasticity and relative viscoelasticity on the basis of different mechanisms. HPMC competed for the interface with soy proteins, but due to its unusual strong surface activity it could dominate the surface pressure and improve film viscoelasticity. The modification of surface pressure and rheological properties of adsorbed soy protein films in the presence of lC necessary suggests the participation of lC + contaminants at the interface. Pure lC could influence the interface by a complexation mechanism, or indirectly by a depletion mechanism in the vicinity of the interface. In addition surface active contaminant of lC if strongly bound to the polysaccharide could bring some polysaccharide molecules at the interface. LB little affected the surface pressure and rheological properties of soy protein films even if surface-active contaminants were present in the commercial preparation. Differences in the interaction of lC and LB gum with the protein should be mainly ascribed to different degrees of incompatibility and to the fact that LB is not charged. Keywords: Soy protein. Gums. Hydrocolloids. Interactions. Interface. Surface pressure. Dilatational rheology. Surface  pressure. Dilatational rheology.