The stabilization of foams by proteins

Abstract

The ability of three crystalline proteins (bovine p-globulin, pepsin and insulin) to stabilize the dispersion of air in water has been studied in two ways : in part 1, by passing air continuously through a protein solution and observing the foam formed and, in part 2, by measuring the average life of individual bubbles formed under the surface of protein solutions and under spread protein monolayers. The effects of changing the protein concentration, pH and ionic strength of the solutions were studied and the results correlated with previous observations on the mechanical properties of films of the same proteins.An attempt is made to explain the observations in terms of three successive processes in the formation of protein films : adsorption, surface denaturation and finally coagulation. It is concluded that only surface-denatured protein is effective in stabilizing the air bubbles.Four general methods are available for investigating the ability of a substance (i) Dynamic method-by studying the rate at which a foam is produced or (ii) Static method-by measuring the rate at which liquid drains from a foam. (iii) SingZe bubble method-by studying the life-time of individual bubbles blown under the surface of the solution.(iv) Size-distribution method4 method which follows the change in surface area of the foam with time is probably the most fundamental but is the most tedious in practice.to stabilize the dispersion of air in liquid as a foam : the stationary volume of foam formed under standard conditions.

Effect of foaming temperature and varying time/temperature-conditions of pre-heating on the foaming properties of skimmed milk

“…Although this problem still exists, the goal of the present study is different. Most of the papers published during the last three decades report on the foaming properties of isolated milk proteins (Anand & Damodaran, 1996;Clarkson, Cui, & Darton, 1999a, b;Cumper, 1953;Damodaran, 2005;Damodaran & Paraf, 1997;Dickinson, 2003;German & Phillips, 1994;Graham & Phillips, 1976;Halling, 1981;Kinsella & Phillips, 1989;Walstra & de Roos, 1993). However, only a few authors deal with the foaming behaviour of milk containing a complex system of different proteins.…”

Investigation of protein foams obtained by bubbling

“…[7] temperature time time necessary to attain the equilibrium surface tension (~o --~o)/(G0 --~,) equilibrium volume of the foam volumetric gas flow rate coordination number in eq. [4] surface concentration of the surfactant surface pressure foaminess surface tension bovine serum albumin critical micelle concentration [A2]…”

“…The foam stability is mainly caused by the film cohesion and film elasticity (4). The rate of surface denaturation at a clean interface is rapid and probably does not vary greatly from one protein to the other, although it does depend upon the pH of the solution, but there are much larger differences in their rates of coagulation which are strongly effected by mechanical agitation to which the film is subjected and by electrostatic forces between the polypeptide chains (4, 6).…”

“…(1)). It has been known long time ago that foams are stabilized by proteins (2,3) and protein foams are influenced by pH and salts (3,4).…”

Interfacial Behavior of Wheat Puroindolines: Study of Adsorption at the Air–Water Interface from Surface Tension Measurement Using Wilhelmy Plate Method

“…The interfacial films are formed only by extended amphiphilic polymer segments of adsorbed unfolded proteins, rather than by compact native structure (16). The foamability of globular proteins is directly correlated with their capability to accumulate at the air-water interface as positive excess (17)(18)(19) and is a qualitative measure of how easily protein molecules are unfolded by shear stress and exposure to the air-water interface.…”