Gel Emulsion Formation

In this chapter, a summary of the structural aspects and the most relevant properties (stability, rheology and diffusion) of gel emulsions is given in section 11.2. It will be followed by a description of gel emulsion formation (section 11.3)... 

Relationship between Phase Behaviour and Spontaneous Gel Emulsion Formation... 

When the process of spontaneous gel emulsion formation, depicted in Figure 11.13, was followed by conductivity as a function of time, a monotonic decrease in conductivity of about four orders of magnitude in a short period of time (less than one minute) was observed when the O/W microemulsion (Figure 11.13a) was... 

The mechanism of 0/W gel emulsion formation was determined " by studying the phase behaviour of gel emulsion-forming systems as a function of temperature and following the emulsification process conductimetrically, as for W/0 gel emulsions. The phase diagram of 0.1 m NaCl aqueous solution/Ci2E06/monolaurin/ -decane as a function of temperature and brine concentration is shown in Figure 11.17. Monolaurin was added to the system to increase the lateral interactions of the surfactant layer and consequently to enhance the stability of the gel emulsions. ... 

Formation and transport of radon ) In the present work, lead isotopes were chemically separated from the sample gas as lead sulfide since the formation of lead sulfide was inevitable under the presence of H2S in the fumarolic gas. The lead sulfide was then dissolved in a small amount of concentrated HCI and mixed with the Insta Gel(emulsion scintillator solution, Insta Gel, Packard Inc.) for the liquid scintillation counting. The chemical yield and the volume of the collected non-condensing gas were obtained from the measurement of the activities of Pb-214 and its progeny which were in radioequilibrium with their precursor Rn-222 whose concentration was determined separately by the direct method. 

H. Kunieda, Y. Fukui, H. Uchiyama, and C. Solans Spontaneous Formation of Highly Concentrated Water-in-Oil Emulsions (Gel-Emulsions). Langmuir 12,2136 (1996). 

C. Solans, R. Pons, and H. Kunieda Gel Emulsions - Relationship between Phase Behaviour and Formation. In B. P. Binks (ed), ModemAspects of Emulsion Science. The Royal Society of Chemistry, Cambridge (1998). 

A general approach for preparing hollow spheres of mesoporous materials was based on sol-gel/emulsion technologies or the use of organic polymer beads as the templates that control the void formation and its volume. 

Figure 3 V Influence of a gel network on SLM stability (A) without gel network SLM degradation by emulsion formation (due to local deformation of LM phase in the pores of the support) (B) homogeneous gel network in LM phase and (C) one thin dense gel layer at the interface with the feed. From Ref. [83] with permission. 2008 Elsevier.

Another consequence of the addition of fatty alcohols to cationic surfactants is the formation, under the right conditions, of liquid crystal and gel networks [41-45] that can greatly increase viscosity and confer stability upon the emulsion. Formation of such liquid crystals has been observed even at low concentrations [44,45] the ready formation of these structures, along with low cost, improved stability, and compatibility with cosmetic ingredients are important reasons why long-chain alcohols are so ubiquitous in conditioning formulations. 

Fig. 6.5.10 Schematic representation of a possible reaction model for aldolase-catalyzed carbon-carbon bond formation in W/0 gel emulsions. A aldehyde acceptor B donor...

Solans C, Pons R, Kunieda H (1998) Gel emulsions - relationship between phase behavior and formation. In Binks BP (ed). Modern aspects of emulsion science. The Royal Society of... 

We have shown elsewhere that sol-gel microparticle formation is one case in which soft matter is used to template the resulting porous material in a basic chemical strategy for making functional nanomaterials using lyotropic mesophases, foams and emulsion, that has been named by Ozin nanochemistry. "... 

In the emulsion technique, solutions are mixed and dispersed into a nonmiscible phase. For food applications, vegetable oils are used as the continuous phase. In some cases, emulsifiers are added to form a better emulsion, since such chemicals lower the surface tension, resulting in smaller droplets. After emulsion formation, gelating and/or membrane formation is initiated by cooling and/or addition of a gelling agent to the emulsion, or by introducing a cross-linker. In a last step, the gel particles formed are washed to remove oil (Chan et al., 2002). 

Kunieda, H., Solans, C., Shida, N., and Parra, J.L (1987) The formation of gel emulsions in a water/nonionic surfactant/oil system. Colloids Surf, 24, ITS-W. 

Kunieda, H., Fukui, Y., Uchiyama. H., and Solans, C. (1996) Spontaneous formation of highly concentrated water-in-oil emulsions (gel-emulsions). Langmuir, 12, 2136-2140. 

The broad diversity in functionality of carbohydrates also offers substantial opportunity for than to influence the mass transport of flavorants. Their ability to form gels, impart viscosity, or promote emulsion formation in food systems are all factors that influence mass transport (dynamic release during eating) of odorants during eating. This section of this chapter will provide an overview of how carbohydrates will influence flavor release from foods. Discussion is organized by carbohydrate type. 

A solvent mixture of chloroform/methanol (2 + 1 v/v) is suitable for a quantitative extraction of lipids. Addition of a small amount of BHA (cf. 3.7.3.2.2) is recommended for the stabilization of lipids against autoxidation. Nonlipid impurities were earlier removed by shaking the extracts with a special salt solution under rather demanding conditions. An improved procedure, by which emulsion formation is avoided, is based on colunm chromatography with dextran gels. 

Gel Emulsions—Relationship between Phase Behaviour and Formation e/s... 

Gel emulsions can be prepared by the usual preparation method for W/O emulsions, dissolving a suitable emulsifier in the component that will constitute the continuous phase followed by addition of the component which will constitute the dispersed phase, with continuous stirring. However, they can be prepared according to several other methods that have been proposed specifically for highly concentrated emulsions.In the following, attention will be focused on the multiple emulsion method and spontaneous formation method, - because they constitute interesting novel methods of preparation. 

In the spontaneous formation method, emulsification is achieved by a rapid temperature change of a micellar solution or microemulsion without the need for mechanical stirring.It should be noted that for W/0 gel emulsions the system is below the HLB temperature at the start and emulsification takes place when an O/W microemulsion is rapidly heated from temperatures below to above the HLB temperature. Formation of O/W gel emulsions, by this method, is achieved by quickly cooling a water-in-oil microemulsion from a temperature higher than the HLB temperature of the system to a temperature below it, at which two phases, a micellar solution phase and an oil phase, appear. The emulsification process for a gel emulsion of the W/0 type is depicted in Figure 11.13. 

Figure 11.16 Schematic change in the spontaneous curvature of surfactant layers in the process ofspontaneous formation of W/O gel emulsions (Reproduced by permission of the American Chemical Society from ref. 40)...

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