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Destabilization mechanisms

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. [Pg.435]

Studies of flow-induced coalescence are possible with the methods described here. Effects of flow conditions and emulsion properties, such as shear rate, initial droplet size, viscosity and type of surfactant can be investigated in detail. Recently developed, fast (3-10 s) [82, 83] PFG NMR methods of measuring droplet size distributions have provided nearly real-time droplet distribution curves during evolving flows such as emulsification [83], Studies of other destabilization mechanisms in emulsions such as creaming and flocculation can also be performed. [Pg.452]

The complex hierarchy of native protein structure may be disrupted by multiple possible destabilizing mechanisms. As has been described in the foregoing, these processes may disrupt noncovalent forces of interaction or may involve covalent bond breakage or formation. A summary of the processes involved in the irreversible inactivation of proteins is illustrated in Fig. 3 and described briefly in the following section. Detailed discussions of mechanisms of protein desta-... [Pg.699]

Destabilization Mechanism of Alzheimer s Ap42 Protofibrils With a Small-Molecule Inhibitor A Molecular Dynamics Simulation Study... [Pg.95]

In the EC process, the destabilization mechanism of the contaminants, particulate suspension, and breaking of emulsions may be summarized as follows. (1) Compression of the diffuse double layer around the charged species by the interactions of ions generated by oxidation of the sacrificial anode. (2) Charge neutralization of the... [Pg.245]

This proposal of a ground state destabilization mechanism for ODCase (this type of mechanism was referred to earlier by Fersht as electrostatic stress 81 and by Jencks as the Circe effect ) sparked considerable controversy. In some circles it was seen as a prime example of the catalytic power of ground state destabilization,83 but several groups immediately questioned its validity on the basis of theoretical objections and apparent inconsistencies with biochemical experiments.23 26... [Pg.206]

Foam stability is most commonly monitored by following its collapse and liquid drainage. Both are macroscopic properties and can easily be measured. These properties are not directly related to microscopic events such as drainage occurring from lamellae, but they allow a description of foam behaviour over time, and, in conjunction with the transient development of bubble size distributions (BSD), yield a complete description of foam destabilization mechanisms (Hailing 1981 Bisperink et al. 1992 Patino 1995 Lau and Dickinson 2005). The common parameter characterising foam stability is half-life time for liquid drainage or foam collapse (Deeth and Smith... [Pg.298]

The above description of foam destabilization mechanisms is only applicable to liquid foods. In solid dispersions, these mechanisms are significantly slowed or even eliminated. As mentioned earlier, solid matrixes such as aerated confectionery wiU hold air for up to years. Structure stabilization occurs for example in chocolate foams when the product is cooled to solidify and trap the bubbles formed within. The baking... [Pg.299]

The stability of emulsion and foam films have also been found dependent upon the micellar microstructure within the film. Electrolyte concentration, and surfactant type and concentration have been shown to directly influence this microstructure stabilizing mechanism. The effect of oil solubilization has also been discussed. The preceding stabilizing/destabilizing mechanisms for three phase foam systems have been shown to predict the effectiveness of aqueous foam systems for displacing oil in enhanced oil recovery experiments in Berea Sandstone cores. [Pg.161]

Ostwald ripening obviously depends on particle polydispersity. If all the particles have the same size, there is no reason for one to grow at the expense of another. Ostwald ripening is also a function of the solubility of the oil in water and of the diffusion coefficient. This provides an excellent means to reduce its effect. The addition of a moderate amount of a water-insoluble oil such as a triglyceride is usually enough to reduce the impact of this destabilization mechanism. [Pg.70]

Flocculation is the mutual aggregation of colliding droplets. In stationary emulsions, droplet collisions arise from Brownian motion (small droplets) and/or from the creaming/sedimentation process (larger droplets). In the latter, the mechanism is often referred to as sedimentation/creaming flocculation. Finally, droplet aggregation can also occur in sheared emulsions. It is important to point out that the droplet size distribution is not altered by the flocculation and creaming/sedimentation destabilization mechanisms. [Pg.385]

Figures 3.12.1 and 3.12.2 illustrate the destabilizing mechanisms involved. Because of the anisotropy of thermal conductivity, a thermal fluctuation of the director along y creates warmer (-I-) and cooler (—)... Figures 3.12.1 and 3.12.2 illustrate the destabilizing mechanisms involved. Because of the anisotropy of thermal conductivity, a thermal fluctuation of the director along y creates warmer (-I-) and cooler (—)...
Emulsified systems can be classified aceording to their thermodynamie stability and their droplets size. Macroemulsions (or simply emulsions) are metastable systems, i.e., the system is not in thermodynamic equilibrium, and it will breakdown into two distinct phases if suffieient time is allowed. However, emulsions that keep their kinetic stability for periods of months or years ean be prepared by using appropriate components and amounts (McClements et al., 2007). This is the most common type of emulsion, and it is found in many food systems such as milk and salad dressing. Macroemulsions are usually polydisperse, with droplet sizes in the range of 1-100 pm. The main destabilization mechanisms in macroemulsions are droplets creaming, flocculation, and coalescence. [Pg.664]


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See also in sourсe #XX -- [ Pg.405 ]

See also in sourсe #XX -- [ Pg.405 ]




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