title: Effect of sucrose on functional properties of soy globulins: adsorption and foam characteristics.
abstract: In this contribution, we have analyzed the effect of sucrose on dynamic interfacial (dynamic surface pressure and surface dilatational properties) and foaming (foam capacity and foam stability) characteristics of soy globulins (7S and 11S). The protein (at 1 x 10(-3), 1 x 10(-2), 0.1, and 1 wt %) and sucrose (at 0, 0.25, 0.5, and 1.0 M) concentrations in aqueous solution and the pH (at 5 and 7), and ionic strength (at 0.05 and 0.5 M) were analyzed as variables. The temperature was maintained constant at 20 degrees C. We have observed the following. (i) The dynamics of adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depend on the peculiar molecular features of proteins (7S or 11S soy globulin) and the level of association/dissociation of these proteins by varying the pH and ionic strength, as well as the effect of sucrose in the aqueous phase on the unfolding of the protein. The rate of adsorption increases with the protein concentration in solution, at pH 7 compared to pH 5, at high ionic strength, and in the absence of sucrose. (ii) The surface dilatational properties reflect the fact that soy globulin adsorbed films exhibit viscoelastic behavior. The surface dilatational modulus increases at pH 7 compared to pH 5, but decreases with the addition of sucrose into the aqueous phase. (iii) The rate of adsorption and surface dilatational properties (surface dilatational modulus and phase angle) during adsorption at the air-water interface play an important role in the formation of foams generated from aqueous solutions of soy globulins. (iv) The increased interfacial adsorption (at high surface pressures) and the combined effects of interfacial adsorption and interfacial interactions between adsorbed soy globulin molecules (at high surface dilatational modulus) can explain the higher stability of the foam, with few exceptions.
authors.affiliation: Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, Sevilla, Spain.
authors.forename: Victor Pizones
authors.initials: VP
authors.lastname: Ruíz-Henestrosa
authors.forename: Cecilio Carrera
authors.initials: CC
authors.lastname: Sánchez
authors.forename: Juan M
authors.initials: JM
authors.lastname: Rodríguez Patino
mesh_terms: D000327:Adsorption; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005916:Globulins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D017510:Protein Folding; D012996:Solutions; D013025:Glycine max / Q000737:chemistry*; D013395:Sucrose / Q000008:administration & dosage*; D014867:Water
chemical_list: D005916:Globulins; D012996:Solutions; D014867:Water; D013395:Sucrose