The interfacial behaviours of the two main pea globulins (legumin and vicilin) at water/air interfaces were studied in order to improve the general knowledge concerning the physicochemical basis of the foaming and emulsifying properties of these proteins. The surface tension (7) was monitored by the WILHELMY plate technique till it reaches a constant value. The final concentration c of the proteins injected in the subphase was comprised between 0.3 . and 80 . lo-" g/ml. The adsorption kinetics ^J = f i r ) were analyzed using different mathematical relations given in the literature. Different phases can be distinguished, corresponding to the diffusion, penetration and rearrangement of protein molecules at the interface, each phase being characterized by a rate constant and an energy barrier.
The rate constants were generally higher in the case of vicilin ; in consequence the equilibrium surface pressure n were reached more quickly. The isotherms x. = Alog c) showed that the concentration needed to reach the plateau value of R , were respectivelyabout 11.7 . 10 ' g/ml and 18.5 . lo-' g/ml for vicilin and legumin at air/water interface. The plateau value of R , was about the same for both proteins at air/water interface (24.5 mN/m). For lower concentrations, vicilin gave higher values for ne. The areas per molecule in the adsorbed monolayer were about the same for vicilin (1.05 nm2) and legumin ( I .04 nm') at air/water interface.
By studying the surface properties of vicilin/legumin mixtures it was observed that ne increased with increasing relative concentration of vicilin and that inhibiting interactions occured between the two globulins, legumin adsorption being more disturbed by vicilin than the opposite.
According to these results, the differences between legumin and vicilin can be related to their molecular characteristics. Pea globulins and especially vicilin appeared to be efficient proteins as surface active agents.