Complex emulsion stabilization

The complex interfacial dilational modulus ( ) is a key fundamental property governing foam and emulsion stability. It is defined as the interfacial tension increment (da) per unit fractional interfacial area change (dA/A) i.e.,... 

McClements, 2006 Anal et al., 2008). Different combinations of proteins and polysaccharides (e.g., P-lactoglobulin + pectin, carrageenan or alginate casein + pectin) have been investigated within the context of multilayer emulsion stabilization (Guzey and McClements, 2006). It seems that the main technical challenge associated with the utilization such complex formation for layer-by-layer emulsion stabilization is the avoidance of bridging flocculation (McClements, 2005, 2006). 

Dickinson, E., Galazka, V.B. (1991). Emulsion stabilization by ionic and covalent complexes of p-lactoglobulin with polysaccharides. Food Hydrocolloids, 5, 281-296. 

Figure 3.5 Demonstration of correlation between the stickiness of protein-coated droplet pair encounters in shear flow (left ordinate axis) and viscoelasticity of concentrated emulsions (right ordinate axis) with the strength of protein-protein attraction as indicated by the second virial coefficient A2 determined from static light scattering , percentage capture efficiency (0%) A, complex shear modulus (G ) for emulsions stabilized by asl-casein or (3-casein (pH = 5.5, ionic strength in the range 0.01-0.2 M).

Dickinson, E. (2008b). Emulsification and emulsion stabilization with protein-polysaccharide complexes. In Williams, P. A., Phillips, G.O. (Eds). Gums and Stabilisers for the Food Industry 14, Cambridge, UK Royal Society of Chemistry, pp. 221-232. 

Two groups of elements appear in significant concentrations in the original crude oil, associated with well-defined types of compounds. Zinc, titanium, calcium, and magnesium appear in the form of organometallic soaps with surface-active properties, adsorbed in the water-oil interfaces, and act as emulsion stabilizers. However, vanadium, copper, nickel, and part of the iron found in crude oils seem to be in a different class and are present as oil-soluble compounds (Reynolds, 1997). These metals are capable of complexing with pyrrole pigment... 

The formation of complexes affects both particle-solvent and particle-particle interactions. The solubility of proteins may be increased by their electrostatic complexing with anionic polysaccharides. Formation of titration-complexes may increase protein solubility and inhibit protein precipitation at the lEP. Anionic polysaccharides can act as protective hydrocoUoids inhibiting aggregation and precipitation of like-charged dispersed protein particles, for example, of denatured proteins. This protective action also can increase the stability of protein suspensions and oil-in-water emulsions stabilized by soluble protein-anionic polysaccharide complexes. 

Bioadhesive color dispersant complexing agent emulsion stabilizer film former viscosity-increasing agent. 

Many dithiocarbamate complexes of zinc, silver, cadmium or mercury improve emulsion stability, including bis(dibenzyldithiocarbamato)-zinc(II) or -cadmium(II) and silver(I) diethyldi-thiocarbamate. Cadmium salts, mixed with citric acid or tartaric acid and added to the emulsion, are reported to be effective. Mercury(II) complexes of ethylenediaminetetraacetic acid (EDTA) and related ligands and of solubilized thiols such as (4) can be used. Other coordination compounds reported include EDTA and related ligand complexes of Co and Mn, mixtures of Co salts with penicillamine (5) and macrocyclic complexes of Ag such as (6). The latter compounds may be used in diffusion transfer systems in which transferred maximum densities are stabilized. 

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