Adsorption and foaming characteristics of soy globulins and tween 20 mixed systems

The manufacture of food dispersions (emulsions and foams) with specific quality attributes depends on the selection of the most appropriate raw materials and processing conditions. In this contribution, we have analyzed the addition of Tween 20 (at 5 x 10(-6) and 1 x 10(-1) M, lower and higher than the critical micelle concentration, CMC, respectively) to improve the dynamic interfacial characteristics (adsorption and surface dilatational properties) and foam properties (foam capacity and stability) of soy globulin (7S and I IS at 0.1 wt %) acidic aqueous solutions. We have observed that (i) the adsorption (presence of a lag period, diffusion, and penetration at the air-water interface) of soy globulins depends on three factors: first the particular protein, second, the level of association/dissociation of these proteins by varying the pH (pH 7 was included as a control), and, finally, on the competitive adsorption between protein and Tween 20 in the aqueous phase. (ii) The surface dilatational properties reflect the fact that soy globulin and Tween 20 adsorbed mixed films exhibit viscoelastic behavior. The surface dilatational modulus decreases with the addition Tween 20 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. However, the stability of the foam correlates with the properties of the film at long-term adsorption.