Foaming capacity and stability

A study of the foaming capacities and stabilities [10] of a variety of air-entraining agents in a solution of cement extracts showed that commonly used anionic air-entraining agents, such as sodium dodecyl sulfate and sodium resinate (1) were visually precipitated from solution, (2) retained their ability to form stable foams after precipitation with only minor amounts of admixture left in solution, and (3) lost the major part of their ability to form stable foams after filtration. It was further shown from studies in cement pastes firstly that the admixture should be adsorbed on the solid particles of the paste with the non-polar ends of the molecule pointed towards the water phase, imparting a hydrophobic character to the cement... 

Foam capacity and stability were increased by increasing... 

Empirical multiple linear regression models were developed to describe the foam capacity and stability data of Figures 2 and 4 as a function of pH and suspension concentration (Tables III and IV). These statistical analyses and foaming procedures were modeled after data published earlier (23, 24, 29, 30, 31). The multiple values of 0.9601 and 0.9563 for foam capacity and stability, respectively, were very high, indicating that approximately 96% of the variability contributing to both of these functional properties of foam was accounted for by the seven variables used in the equation. 

Multiple linear regression equations were also developed for foam capacity and stability based on pH and the data on composition of soluble and insoluble fractions in the suspensions sumarized in Figures 2 and 4 (Tables V and VI). 

Multiple r2 values of 0.9346 and 0.9280 were obtained for these equations of capacity and stability, respectively. The relative importance of each respective partial regression coefficient was determined by comparison of B values (32). These evaluations indicate that the most important variables in the two models for foam capacity and stability are soluble protein, soluble and insoluble carbohydrate and ash, and insoluble fiber. 

The experimental data in Figures 2 and 4 were used in multiple regression equations to predict foam capacity and stability of 2% to 30% suspensions adjusted to pH values of 1.5 to 11.5 (Figures 6 and 7). Observed and predicted data of the... 

The smallest increases in foam capacity occurred at pH 6.7. Percentages of protein in the soluble fractions varied at this pH. Foam capacity and stability improved and decreased, respectively, at this pH as the salt content of the suspension was increased. The two-step pH adjustment (23) of 6.7 to 4.0 to... 

Foaming Capacity and Stability. Pepsin digestion of soy protein has been proposed as a method for making a whipping protein for egg albumen replacement (42, 45) and for extenders for albumen in bakery and confectionery formulations (46). Puski... 

Foam stability showed little variation among suspensions at pH 1.5 and 4.0, remaining between 35% and 45% (Figure 7). The largest variations In stability were noted among suspensions at pH 6.7 and 8.2, and after the two-step adjustment to pH 6.7. Increasing the amount of salt In the suspension at these pH values decreased foam stability. The suspensions adjusted from pH 6.7 to 4.0 to 8.2 exhibited similar foam capacity and stability, regardless of salt concentration. 

For the studies presented in this chapter, samples of peanut and cottonseed meal suspensions were evaluated for foam capacity, stability, and viscosity measurements as described by Cherry and coworkers (23, 24, 22). Vegetable protein suspensions at the appropriate concentration and pH were whipped in a Waring-type blender. After blending, the whipped products were transferred to a graduated cyclinder. Milliliters of foam were recorded immediately and at various time intervals to determine capacity and stability. A Brookfield viscometer and... 

For this reason, some American wineries have adopted the use of products that increase surface tension. This process reduces foam formation and stability. Two anti-foaming agents are gaining popularity dimethyl polysiloxane and a mixture of oleic acid mono- and diglyceride. They are used at a concentration of less than 10 mg/1 and do not leave a residue in wine, especially after filtration. Due to their efficiency, red wine tanks can be filled to 75-80% capacity and white wine tanks to 85-90%. These products are not toxic. The Office International de la Vigne et du Vin recommends the exclusive use of the mixture of oleic acid mono-and diglyceride. 

Alcohol sulfates are excellent foaming surfactants. According to the Kitchener and Cooper classification [148], alcohol sulfates form metastable foams. However, quantitative values cannot easily be compared because foam largely depends not only on the instrument used to produce and evaluate foam but also on the concentration of surfactant, impurities, temperature, and many other factors. In addition, a complete characterization of the foam capacity should take into account the initial amount of foam, its stability, and its texture. 

Foam properties related to salt. The addition of sodium chloride to soybean protein suspensions caused them to form high-capacity, low-stability foams (13). It was suggested that foam capacity increased because salt improved protein solubility at the interface of the colloidal suspension during foam formation, but retarded the partial denaturation of the surface polypeptides of proteins that are necessary for protein-protein interaction and stability. 

Food foams are usually made by bubbling, whipping, or shaking a protein-containing solution. Several measures of foaming capacity of proteins and other stabilizing agents exist, such as overrun, which quantifies the amount of foam produced, defined as ... 

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