STABILITY AND MECHANICAL STRENGTH OF AQUEOUS FOAMS CONTAINING FOOD PROTEINS

The role of proteins in the formation and stabilization of foams is im portant in many food applications. Most such products are made with eg g white or milk proteins as emulsifiers. This study is concerned with the foaming properties of high-quality caseins and ovalbumin, as model food systems. The foaming properties (foam strength and stability) we re evaluated in an aeration column (bubbling method). Foams were gener ated with several well-known food proteins: casein, acid casein, sodiu m caseinate, calcium caseinate, and ovalbumin. Experimental conditions varied as follows: (a) temperature between 5 and 40 degrees C; (b) pr otein concentration from 0.01 to 1% (w/w); (c) pH between 2 and 9; and (d) ethanol and sucrose were added to distilled water to produce solu tions of concentrations between 0 and 1 M. A second-order kinetics mod el is a satisfactory mathematical description of the foam drainage beh aviour, so the discussion of the results is based on the second-order rate constant for drainage. It was observed that intrinsic molecular p roperties (the nature and extent of protein-protein interactions), as well as environmental and processing factors (temperature, pH and visc osity of the continuous phase) affected the foaming properties. Moreov er, foams with enhanced mechanical strength (greater protein-protein i nteractions) were more stable.