Foaming ability

The many uses of egg products are basically a result of three properties of eggs coagulation when heated foaming ability (whippability) and emulsifying properties. The coloring ability and aroma of egg should also be mentioned. 

Egg white begins to coagulate at 62 °C and egg yolk at 65 °C. The coagulation temperature is influenced by pH. At a pH at or above 11.9 egg white gels or sets even at room temperature, though after a while the gel liquiefies. All egg proteins coagulate, except ovomucoid and 

Whipping of egg white builds a foam which entraps air and hence is used as a leavening agent in many food products (baked goods, angel cakes, biscuits, souffles, etc.). 

The whipping properties of dried egg white can be improved by the addition of whey proteins, casein and bovine serum albumin. The foaming ability is also increased by weak proteolysis and partial hydrolysis of the oligosaccharides in the glycoproteins by treatment with amylases. 

The whippability of egg white can be assayed by measurement of foam volume and foam stability (amount of liquid released from the foam in a given time). 

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Chlebicki and Slipko [127] determined the foam ability of sodium propoxyl-ated alcohol sulfates by the Ross-Miles method. These substances are low-foaming surfactants the greatest foam height was observed for dodecyl and tetradecyl chains. As expected, as the number of polyoxypropylene units on the same alcohol chain increases, foam height decreases. The maximum foam height obtained was 225 mm for a 2 g/L solution of sodium tetradecyl (1 PrO) sulfate. 

The foaming ability of a liquid mixture depends on the magnitude of the variation of surface-tension with concentration, but not on its sign 95). In practice, however, the effect of surface tension on plate efficiency... 

With regard to miscible polymers, simple blending allows one to develop materials that frequently reveal an intermediate behavior between those of the individual blend components [2, 3], Such systems can be easily exploited for fine-tuning the foam-ability, for example by controlling important foaming parameters such as the melt rheology or the gas solubility. 

Reichelt N, Stadlbauer M, Folland R, Park CB, Wang J (2003) PP-blends with tailored foam-ability and mechanical properties. Cell Polym 22 315-327... 

Non-ionic surfactants do not exhibit Krafft points. Rather the solubility of nonionic surfactants decreases with increasing temperature and the surfactants begin to lose their surface active properties above a transition temperature referred to as the cloud point. This occurs because above the cloud point a separate surfactant-rich phase of swollen micelles separates the transition is visible as a marked increase in dispersion turbidity. As a result, the foaming ability of, for example, polyoxyethyle-nated non-ionics, decreases sharply above their cloud points. The addition of electro-... 

The tests used to determine antifoaming and defoaming action are essentially the same as used for testing foaming ability (see Section 2.6.2), except that the prospective defoaming agents are added in measured amounts and in a reproducible manner. 

Most manufacturers are very interested in utilizing optimum performances to make advertising claims and, therefore, will evaluate a large number of soils. The choice of high nonionic/alkylbenzene sulfonate ratio as compared to a reverse high alkylbenzene sulfonate/nonionic ratio again depends upon the choice of foaming ability and the choice of soils to be removed. 

The foaming capacity of succinylated soy protein was significantly better than those of the unmodifided proteins. Foam volumes progressively increased with pH from 3 to 10 (12). Succi-nylation caused a small increase in foaming capacity of cottonseed flour (38). Solubility is required for the production of protein foams (48), and succinylation substantially increased the foaming ability of soy isolate by enhancing their solubility. 

In the pour test [43] foam is obtained by pouring the solution tested through a calibrated orifice from a definite height on the surface of the same solution (Fig. 1.5). This method has been studied in details and has been adopted in several countries as a standard one for estimation of foaming ability of a solution (for example, solutions of detergents). This method has various modifications [5,6,8],... 

For a comparative estimation of the foaming ability of beer and soap solutions other similar characteristics are used, for example residual foam (R.F.) [15]... 

Definition of the Term Foam Stability and Foaming Ability of Solutions... 

The kinetics of foam collapse, i.e. the process of gas and liquid separation, is characterised by the rate of reduction of foam volume with time or by the rate of decline in its height, if the cross-sectional area is equal along the whole foam column. The stability of the foam as a whole can be characterised quantitatively at any moment by the reciprocal quantity of the rate of foam column destruction. Most often, however, the estimation of the stability of the foam column, is expressed by an integral characteristic time of decay of the whole foam column or a part of it. The relation between the internal foam collapse and the destruction of the foam column is discussed in Section 6.5. Sometimes foam stability is considered in terms of foaming ability of the solution. In general the latter characteristic involves the easiness of foam formation, foam volume and stability. Such an interpretation, however, makes this characteristic rather indefinite. For example, Abramson [12] indicates that for the estimation of the foaming ability of surfactants it is necessary to know the quantity and stability of the foam obtained from a particular surfactant as well as the conditions under which the surfactant acts as a foam stabiliser. That is why it has been repeatedly emphasised that foaming ability... 

The authors of this monograph consider reasonable to express foaming ability as the foam volume obtained from a known solution volume under defined conditions (temperature, surfactant concentration, mode of foam formation). As a more general characteristic of the ability of the surfactant solutions to form foams with a definite stability it is suitable to use the terms stabilising ability or foaming property. The volume of the foam obtained and its lifetime can serve as a qualitative measure for the latter. A more detailed estimation requires the use of a number of characteristics including drainage, internal foam collapse, etc. 

In order to develop efficient techniques for the preparation and application of foams in industry, agriculture, firefighting, etc., it is necessary to know the physicochemical parameters of surfactants and their relationship with the foam stabilising ability of the surfactant solutions. Usually the criterion of the surfactant foaming ability is the adsorption of these compounds at the solution/air interface and the related to it properties, such as decrease in surface tension, adsorption work, maximum adsorption T. [13,39,43]. CMC is often used as a characteristic of a foaming agent (if micellisation is possible in the surfactant solution). Parameters related to foam stability, such as foam lifetime and foam column height, are also employed [12,13,39],... 

The physicochemical characteristics of the foam films and the foam are in good agreement. Thus, Xr for foams stabilised by the members of the homologous series of oxyethylated dodecyl alcohol does not change after n > 10, which is in accordance with the Cw(n) dependence. The effect of the hydrophilic-lipophilic balance on the foaming ability of surfactants will be treated in Section 7.9. 

Dependence of the Foaming Ability on the Mode of Foam Formation and the Properties of the Surfactant Solutions... 

The foaming ability of solutions, characterised by the volume of the foam generated, depends on the composition (including the various stabilising additives), temperature, way of foam generation and the stability of the foam with respect to internal collapse and foam... 

If the dependence between the foam volume and foam stability is known, as in the case of foams produced by barbotage, the foaming ability would serve as a useful characteristics of the surfactant solutions [13], However, since this dependence is not an explicit one and does not comprise foams generated by other means, this characteristic is of little importance. 

Certain antifoams, for example, methyl or ethyl alcohols, when introduced in the foaming solution, affect indirectly the foam stabilising properties of the adsorption layers because they change either the surfactant solubility or its CMC. It has been established [39] that addition of antifoams (2-ethylhexanoI and tributyl phosphate) increases CMC. Schick and Fowkes [40] have observed a certain change in CMC of NaDoS when tetradecanol is added. If the compounds added improve the foaming ability (such as dodecylglycol ether and (3-hydroxyethyl laurylamide), CMC decreases. 

At low surfactant concentrations (for example, the concentrations that are reached at the waste water foam purification from surfactant pollutants) the foaming ability is usually limited by the minimum surfactant concentrations necessary for formation of stable foam films. This concentration is close to the concentration of black spot formation in microscopic films Cbi and black films Cfbu being an important characteristic of the foam stabilising ability of surfactants. The values of Cm for some surfactants are given in Table 3.1 and the dependence of Cm on various factors is considered in Section 3.4. 

An early attempt to correlate the physical properties of surfactant solutions and their foams with oil recoveries was performed by Deming in 1964 (50). Deming concluded that high foaming ability favored high displacement efficiency, but that high foam stability were not required for high displacement efficiency. Bernard and Holm found that oil substantially decreased the abilities of most surfactants to reduce aqueous permeabilities, but that some surfactants remained effective even in the presence of oil (52,53). 

Foaming Ability and Foam Stability. Foaming ability and foam stability were determined in triplicate on 100-mg/mL solutions of freeze-dried raw foam and humic substances from stream, foam, and foam-extract samples. Measurements were made at 25 at pH 3.0, 7.0, and 10.0, with sample pH adjusted using O.IN sodium hydroxide using the Ross Miles method (D1173-53 ASTM standards, 1991). Briefly, a 200-mL... 

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