KINETICS OF DESTABILIZATION OF SOY PROTEIN FOAMS

The kinetics of destabilization of soy protein foams was studied by monitoring the decay of interfacial area of foams as a function of time. The decay of soy protein isolate, soy 11S, and soy 7S foams followed biphasic first-order kinetics. These two kinetic phases were related to gravitational liquid drainage and interbubble gas diffusion processes. The relative magnitude of the contribution of these two microscopic processes to foam decay was dependent on environmental factors such as pH, temperature, ionic strength, and protein concentration. Soy isolate and soy 11S foams were more stable than soy 7S foams. The poor stability of soy 7S foam was mainly due to its inability to retard gravitational drainage.