REPRINTS, COPIES

Attributes to Stabilize Foams
*low interfacial tension
*high viscosity of the bulk liquid phase.

REFERENCES

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Babcock, C.J. 1922July 13. The whipping quality of cream. United States Department of Agriculture. Bulletin No. 1075. Washington, D.C.

ContentsFactors influencing whipping quality; Experimental procedure, Method of comparing stiffness of whipped cream; relation of various factors to whipping quality;"standing-up" quality of whipped cream; whipping quality of powdered cream, whipping quality of evaporated milk; summary.

Cardillo, M.J. 1985. concepts in gas-surface dynamics. Langmuir 1: 4.

Recent experiments and theoretical results treating the dynamics of gas-surface interactions have led to important conceptual developments and generalizations. Examples will be given which include predominately repulsive gas-surface potentials, activated dissociative adsorption, and the relation between thermodynamics and chemical dynamics of desorption.

Dickinson, E. and G. Stainsby. 1987September. Progress in the formulation of food emulsions and foams. Food Technology 41(9):74.

Duxbury, D.D. 1986. Foam control is vital in many foods/beverages. Food Processing. 47(12): 42.

Hung, Y.-C., K.H. McWatters and M.S. Chinnan. 1988. A microscopic method to quantify whippability. Journal of Food Science 53(5): 1566.

Abstract A microscopic method based on stereologic principles was developed to quantify the amount of air in a gas-in-liquid dispersion. Whipped pastes made form cowpeas dried at 50, 70, 90 and 110C were used as the test system. The method effectively demonstrated qualitative and quantitative differences in the samples and correlated well with specific gravity and total foam volume measurements; the correlation coefficients were -0.98 and 0.94, respectively.

Kubota, K., S. Hayash8i, and M. Inaoka. 1983. A convenient experimental method for measurement of zeta-potentials generating on the bubble suspended in aqueous surfactant solutions. Journal of Colloid and Interface Science 95: 362.

Abstract A convenient experimental method is described for measurement of the electrophoretic mobilities or the zeta-potentials of very small air bubbles in surfactant solutions. Air was dissolved into the single-distilled water at a constant pressure of 0.5Mpa. When the pressure was balanced with atmpspheric pressure suspensions consisting of very small bubbles were obtained. The three surfactants sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and cetylpyridinum chloride were dissolved into the suspensions. The suspensions were poured into the conventional microelectrophoresis cell, and the velocities of the bubbles were mesured at the so-called"stationary level," and the zeta-potentials were determined. The experimental curves as a function of the concentrations of surfactants were compared with tose obtained from the method based on the Dorn effect reported previously. The agreement was satisfactory in general trends. Using the experimental potentials and the simple electrical double-layer theory, the surface excesses were calculated and compared with those predicted from the Gibbs adsorption equation combined with the experimental surface tensions. Both adsorption densities or the surface excesses conformed each other in general grends, suggesting the above simple theoretical considerations were confirmed experimentally. using the two different kinds of potential measured, the distances between the slipping planes were also calculated.

Lakes, R. 1987. Foam structure with a negative Poisson's ratio. Science 235: 1038.

Abstract A novel foam structure is presented which exhibits a negative Poisson's ratio. Such a material expands laterally when stretched, in contrast to ordinary materials.

Marmur, A. 1983. Equilibrium criteria for thin fluid films. Journal of Colloid and Interface Science 93(1): 18.

Abstract General equilibrium criteria for thin fluid films are developed and applied, using reasonable assumptions to specific examples. These include a film between two rigid, insoluble, and parallel plates, between a rigid insoluble solid and a fluid phase, between two fluid phases, a soap bubble, and a soap film on a frame. The main physical conclusion is that, under the conditions discussed, a thin fluid film cannot exist in equilibrium with a fluid bulk phase whose surface curvature is appreciably different than that of the film. Implications of the conclusions to wetting, emulsions, and soap films are presented.

Monsalve, A. and R.S. Schechter. 1984. The stability of foams: dependence of observation on the bubble size distribution. Journal of Colloid and Interface Science 97(2): 327.

Abstract The rate of foam collapse owing to interbubble gas diffusion is shown to be a sensitive function of the initial distribution of bubble sizes. Experimental evidence is presented to support these theoretical conclusions. The poor reproducibility of existing foam stability tests can be understood in terms of this sensitivity. The foam surface area decreases as a bilinear exponential function of time. Once of the two characteristic time constants appears to be related to a gravity drainage mechanism while the second one is determined by the rates of gas diffusion between bubbles.

Morrison, I.D. and S. Ross. 1983. The equation of state of a foam. Journal of Colloid and Interface Science 95: 97.

Abstract An equation of state of foam relates the six state variables of volume and pressure, moles of gas and temperature, surface area of liquid and surface tension. The equation for several special cases can be established as
PV + (2/3)omegaA=nRT
Previous attempts to prove this equatin as a universal law, applicable to any foam, are reviewed and shown to be limited in their application. Nevertheless, the probability is high that the equation is indeed generally applicable, although a rigorous proof is still lacking.

Nishioka, G.M., S. Ross and M. Whitworth. 1983. The stability of foam: comparison of experimental data and computed results. Journal of Colloid and Interface Science 95(2): 435.

Abstract The rate of loss of total surface area of a foam contained in a fixed volume at constant temperature may be determined from the measured rate of increase of gas pressure in the head space above the foam. The rate of loss of surface area of foams with different drainage characteristics is reported and compared with computed results based on a model proposed by Lemlich. Lemlich's model can be adapted to computer the decline of total surface area of a foam with time due solely to interbubble gas diffusion. Reasonable agreements between computer and observed data are obtained even when a constant thickness of foam lamellae is assumed; better agreements are obtained if the effects of capillary drainage of interstitial liquid are taken into account.

Phillips, L.G., J.G. german, T.E. O'Neill, E.A. Foegeding, V.R. Harwalkar, A. Kilara, B.A. Lewis, M.E. Mangino, C.V. Morr, J.M. Regenstein, D.M. Smith, and J.E. Kinsella. 1990. Standardized procedure for measuring foaming properties of three proteins, a collaborative study. Journal of Food Science 55(5): 1441.

Abstract A collaborative study involving nine laboratiories was conducted over four years to evaluate a rapid, simple and reliable whipping method for measuring overrun and foam stability. Effectiveness of the method was assessed by meauring the characteristics of foams formed by three protein solutions (5%): sodium caseinate, milk protein isolate, and egg white protein; identifying and systematically eliminating sources of variability. major sources of variability were protein dispersing technique, the mixer, and the care exercised by the oeprator during sampling and weighing. The method detected differences in foam stability between egg white, casein, and milk protein isolate (pooled SD=4.5) using different mixers.

Phillips, L.G., Z. Haque, and J.E. Kinsella. 1987. A method for the measurement of foam formation and stability. Journal of Food Science 52(4): 1074.

Abstract A whipping method for the measurement of ovrrun and foam stability was developed. Using this method the charcteristic foams formed by the following proteins were studied: sodium caseinate, milk protein isolate and whey protien. The method was able to detect differences between foams produced by different proteins. The effects of copper sulfate and proteose-peptone on egg white foams were studied to show the reliability of the method. It was demonstrated that the addition of 1mM copper sulfate stabilized (P<0.05) foams made from both fresh and powdered egg white. addition of proteose-peptone (0.05% and 0.1%) reduced the overrun and destabiized egg whtie foams.

Patel, P.D., A.M. Stripp and J.C. Fry. 1988. Whipping test for the determination of foaming capacity of protein: a collaborative study. International Journal of Food Science and Technology 23: 57-63.

Summary A standard whipping test, which involved preparing a 0.5% protein dispersion, whipping the dispersion in a Kenwood Chef food mixer and measuring the foaming properties (foam expansion, FE; foam volume stability, FVS;' foam liquid stability, FLS,) was collaboratively evaluated. A total of sixty determinations was made involving six laboratories, each of which analysed five samples in duplicate. The repeatability coefficient of variation (Cvo) in the estimation of FE and FVS properties of proteins was less than or equal 6.25%. The reproducibility coeffieicent of variation (Cvs) for FE and FVS was less than or equal 9.8%, excluding the FE value (i.e. 20%) for spray-dried albumen. The Cvo and Cvs values for FLS properties of proteins ranged from 7.4 to 13.4% and 17.2 to 24.6%, respectively. Thus, FE, FVS and FLS properties can be used for intra-laboratory comparisons (e.g. to determine batch-to-batch variation in commercial protein products), whereas FE and FVS values are more reliable for inter-laboratory comparisons of the foaming properties of proteins.

Rosen, M.J. and F. Zhao. 1983. binary mixtures of surfactants. The effect of structural and microenvironmental factors on molecular interaction at the aqueous solution/air interface. Journal of Colloid and Interface Science 95(2): 443.

Abstract Using the nonideal solution treatment developed in a previous publication (Rosen and Hua, J. Colloid Interface Sci. 86: 164(1982)) surface tension-concentration curves for individual purified surfactants and their binary mixtures are used to calculate beta, the molecular interaction parameter for mixed monolayer formation. The value of beta is essentailly constant with change in the value of the mole fraction of either surfactant in the surface phase from 0.2 to 0.8. Maximum interaction between the two surfactants occurs when their alkyl chains have the same number of carbon atoms. There is a decrease in beta with increase in pH of the solution phase for an anionic-polyoxyethylenated nonionic system, consistent with the previously postulated weakly cationic character of the polyoxyethylene chain. With increase in the sodium chloride concentration of the solution, the value of beta decreases for a cationic-polyoxyethylenated nonionic mixture but goes through a maximum for anionic--olyoxytethylenated mixtures. This may be due to complex formation between some ether oxygen of the polyoxyethylene chains and sodium ions. Temeprature increase in the 10-40C range results in a decrease in the value for beta for ionic-polyoxyethylenated nonionic mixtures.

Ross, S. and Y. Suzin. 1973. Measurrement of dynamic foam stability. Langmuir1: 145-149.

Abstract An improved foam test for lubricating oils described by Watkins consists of substituting a cone for a cylinder as the foam vessel. The concept of a conical vessel is based on the supposition that the top area of a dynamic foam should be a variable that enters into its equilibrium condition. Results are reported for several foam systems that incorporate the added feature. A unit of foam stability expressed as the average stay time of gas in the foam is developed and tested for the conical foam meter. A comparison of foam stabilities by a standard method, using cylindrical and conical types of meters, shows that quite different answers for the variation of foam stability with temperature are obtained. There is no"right answer". A foam test should produce foam and measure its stability under conditions similar to those of its ultimate application. The shape of the container is one of the significant conditions.

Shaw, D.J. 1970 (2nd Ed). Liquid-Gas and Liquid-Liquid interfaces. IN Introduction to Colloid and Surface Chemistry Butterworth.

Ternes, R.L. and J.C. Berg. 1984. The effect of monolayer collapse on bubble stabiity. Journal of Colloid and Interface Science 98: 471.

Abstract Measured lifetimes are reported for air bubbles trapped between insoluble monolayers and the bulk aqueous substrate in a Langmuir-Wilhelkmy trough under conditions of constant surface pressure. Results for all films studied, octadecanol and myristic, oleic and gondoic acids, indicate that monolayer collapse is a decisve factor in determining bubble stability. The presence of nascent reservoirs of collapsed film capable of rapid respreading appears responsible for the observed loss of stability. The results also challenge the generally held belief that the stabiity of evanescent bubbles is directly proportional to the Gibbs elasticity of the monolayer.

Vani, B. and J.F. Zayas. 1995. Foaming properties of selected plant and animal proteins. 1995. Foaming properties of selected plant and animal proteins. Journal of Food Science 60: 1025.

Abstract The foaming properties of proteins are important in prediciting their funtionality in aerated foods. In model aqueous systems, foam expansion (FE) and foam stability (FS) of commercial plant proteins, wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF), were compared with those of nonfat dried milk (NFDM) and egg white powder (EWP) at 1,2,4,6, and 8% using one-=and two-way analyses of variance. The effects of pH 4,5,6,7 and 8 on FE and FS of WGPF were also measured. The highest overall FE and FS were obtained for EWP. Among plant proteins, FE and FS were maximum for CGPF and SF, respectively. FS was lowest for NFDM. Except for SF, FE, and FS increased with increasing protein concentration. The FE and FS of WGPF were highest at pH 8, lowest at pH 7, and intermediate at pH 4-6.

Woodburn, M.J. and T.N. Morita. 1978. Staphylococcal enterotoxin and nuclease production in foams. Journal of Food Science 43: 1628.

AbstractAir was incorporated into culture media by the addition of cellulose or nonabsorbent cotton pads to cornstarch pastes and by foam formation in an agar gel. Production of staphylococcal enterotoxin types A, B, and C during incubation at 37C was increased both on a per ml basis and per 10 CFU by such air incorporation but not in deaerated controls. Nuclease production followed the same trend. Cell numbers were less affected. Even limited inclusion of air within a food sytem thus increases the rate of staphylococcal production of entertoxin.

Zaniquelli, M.E.D. and F. Galembeck. 1985. Modification of foam drainage by electroosmotic effect. Langmuir 1: 647-651.

Abstract Electroosmotic liquid mass transfer is observed in air-liquid foams subjected to dc fields in the range of 15-100V cmminus one. Foams were prepared by using aqueous sodium lauryl sulfate solutions and subjected to either vertical or horizontal dc fields. Liquid transfer was monitored by volumetric and conductance measurements. In each case liquid moved toward the cathode, thus affecting spontaneous drainage.

Updated: Sunday, March 30, 2008.