Rheological Method for Kinetics of Drainage and Disproportionation of Soy Proteins Foams

The effect of soy protein (SP) concentration and denaturation on foaming properties was investigated. To measure drainage and disproportionation rates, a special method was based on measurements of time dependency of foam viscosity. Foam expansion reached a maximum at 3% protein concentration for denatured and 5% for native SP. Rates of drainage and disproportionation were greatly decreased by increasing protein concentration due to increased liquid viscosity (drainage) and to lowering of surface tension (disproportionation). Denaturation of SP increased foam expansion and decreased rate of drainage over the concentration range but lowered rate of disproportionation at > 4% protein.