Emulsion particle aggregation

The water solubilities of the functional comonomers are reasonably high since they are usually polar compounds. Therefore, the initiation in the water phase may be too rapid when the initiator or the comonomer concentration is high. In such a case, the particle growth stage cannot be suppressed by the diffusion capture mechanism and the solution or dispersion polymerization of the functional comonomer within water phase may accompany the emulsion copolymerization reaction. This leads to the formation of polymeric products in the form of particle, aggregate, or soluble polymer with different compositions and molecular weights. The yield for the incorporation of functional comonomer into the uniform polymeric particles may be low since some of the functional comonomer may polymerize by an undesired mechanism. 

Creaming Aggregation of lipid emulsion particles that then migrate to the surface of the emulsion that can be reversed with mild agitation. 

Most food products and food preparations are colloids. They are typically multicomponent and multiphase systems consisting of colloidal species of different kinds, shapes, and sizes and different phases. Ice cream, for example, is a combination of emulsions, foams, particles, and gels since it consists of a frozen aqueous phase containing fat droplets, ice crystals, and very small air pockets (microvoids). Salad dressing, special sauce, and the like are complicated emulsions and may contain small surfactant clusters known as micelles (Chapter 8). The dimensions of the particles in these entities usually cover a rather broad spectrum, ranging from nanometers (typical micellar units) to micrometers (emulsion droplets) or millimeters (foams). Food products may also contain macromolecules (such as proteins) and gels formed from other food particles aggregated by adsorbed protein molecules. The texture (how a food feels to touch or in the mouth) depends on the structure of the food. 

Figure 16. Effect of particle aggregation on the back-scattered light intensity profile of food emulsion, containing 20 wt% emulsified fat, at 5 °C (green light).

Particle size and particle aggregate size distribution is now being used for monitoring product stability and functional properties in a range of food emulsion systems24. 

Coating of emulsion particles with cholesterol-bearing polysaccharides, such as pullulan, amylopectin, and mannan, led to a reduction of the divalent metal ion-induced aggregation of Che emulsion droplets. The cholesteryl group behaves as a hydrophobic anchor in the surface lipid layer resulting in a lower fluidity of the. surface of the emulsion droplets (24). 

Based on the DLS measurements it is possible to find particle size distributions of polymers and proteins, particle aggregation phenomena, micellar systems and their stability, micro-emulsion technology, colloid behaviour, nucleation processes and protein crystallization. DLS is a non-destructive and convenient method and so it can find application in various branches of science. In chemistry it finds application in topics of colloids, polymers, emulsions, suspensions, nanoparticles, and in physics, applications such as in astrophysics and atmosphere physics and in biology it involves biophysics and biomedicine applications. 

Fig. 5.75 TEM micrographs of several emulsion particle samples show a range of aggregation. An air dried droplet (A) resulted in agglomerated flat particles. More three dimensional particles would still be difficult to measure as they are touching (B). The emulsion particles (C) are well dispersed and shadowing with chromium clearly shows that they are discrete spheres after freeze drying.

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