Emulsions making

Occasionally when aqueous solutions, and particularly suspensions, are extracted with an organic solvent very unpleasant emulsions make a clean separation impossible. The most effective way of avoiding this difficulty is to mix the liquids carefully. Further remedies are creation of a vacuum in the separating funnel, addition of a few drops of alcohol, saturation of the aqueous phase with common salt,. . . and patience. 

Uses Most important silver salt used in photography emulsion making intensification etc. Caution Stains on fingers can be removed by rubbing with tincture of iodine followed by a strong solution of hypo. 

The ability of proteins to form gels and stable emulsions makes them suitable encapsulant materials for delivery of a range of food components. By controlling the microstructure of the gel network, the release of the entrapped food component (e.g., bioactive) can be manipulated (Chen et al., 2006). 

Ease of manufacture and scale up The spontaneity of formation of micro emulsions makes their manufacturing and scale up very easy as compared to other colloidal carriers such as emulsions or liposomes which require specialised instruments such as high pressure homogenisers for their manufacturing. 

Supersaturation. This is not applied in food emulsion making but is fairly common in foams. A gas can be dissolved in a liquid under pressure, and then the pressure is released, so that gas bubbles are formed. The gas should be well soluble in water to obtain a substantial volume of bubbles, and carbon dioxide is quite suitable. It is applied in most fizzy beverages. C02 can also be formed in situ by fermentation, as in beer and in a yeast dough. Initiation of gas bubble formation is discussed in Section 14.4. 

Note This example illustrates the very poor efficiency of such a beating method with respect to energy use. In industrial machines for foam or emulsion making a higher efficiency can be obtained, though rarely over 0.3%. 

Small volume concentrations of water in the emulsion make it possible to limit the analysis to the motion of isolated drops, ignoring their influence on each other and on the continuous phase. Since trajectories of drops are curved only near electrode, it suffices to consider the behavior of drops in the immediate vicinity of the electrode elements, that is, near cylindrical wires. The motion of charged particles flowing around a single cylindrical electrode has been considered in [102]. 

S TorandeU. Extrapolation de conditions operatoires de fabrication d emulsions cosmetiques lors du passage de I echelle laboratoire aux echeUes pilote et industrieUe [Extrapolation of operating conditions for cosmetic emulsion making from laboratory scale to pilot and industrial scales]. PhD dissertation, Institut National Polytechnique de Lorraine, Nancy, France, 1999. 

Stability depends upon so many things that it is easy to alter its value. However, in most eases the general phenomenology versus formulation and eomposition is valid. The presenee of aleohol, partieularly an intermediate-solubility alcohol, such as rec-butanol or ter-pentanol, or a mixture of propanol and butanol, tends to reduce the interfacial adsorption of the surfactant, thus reducing all associated effects, in particular the repulsion that eontributes to stabilization. It is worth noting that the use of mixed surfae-tant systems, which is often advised in emulsion making manuals, can be detrimental in some eases in which a selective partitioning of surfactant species takes plaee (191, 192), and little surfactant is left at the interfaee. 

These hysteresis areas are found at die limit of die normal and abnormal regions, and exhibit a typical wedge shape that vanishes as SAD = 0. From the practical point of view of emulsion making these features are quite useful. For instance, by starting in a normal A region and increas-... 

Antibacterial and antifungal activities Thickening polymer Role on surfactant stability stabilize emulsion Make hair softer, increase mechanical strength Protecting elastic film on hairs, increasing their softness lacquers. Hair sprays Time release deliveries (chitosan beads, gels or granules)... 

Capillary effects are encountered in many areas of interface and colloid science, with its importance relative to other processes (e.g., fluid dynamics) depending on the exact situation. For example, when two spherical drops of a liquid in an emulsion make contact and coalesce to form a larger drop (Fig. 6.2a), the extent and duration of flow due to the capillary phenomenon is limited and fluid dynamics is of little practical importance. When there is an extensive amount of flow, on the other hand, such as in capillary imbibition, wicking processes, or capillary displacement (Fig. 6.2b) fluid dynamics may become important. 

In practical emulsions, the sensitivity and reciprocity behavior are usually greatly increased by sensitizers, compounds that are added during emulsion-making and are adsorbed on the surface of the crystals. Chemical sensitization produces a major decrease in the number of absorbed photons needed to make a crystal developable and can greatly decrease low-intensity reciprocity failure. Care must be exercised, however, since too much sensitization can cause the formation of chemical nuclei that can act like LI during development, giving rise to fog (spurious density in nonexposed areas). 

To make silicone fluids useful in aqueous systems, there are various emulsions available. The use of an emulsion makes it easier to handle, and use in formulations, but there are issues related to emulsion stability, which must be addressed. Specifically, the addition of surfactants by the formulator to a purchased emulsion may shift the Hydrophile-Lipophile Balance (HLB) and split the emulsion. 

Inlroduction and Definitions ]l. Emulsion Making Importance of Formulation 111. Formulation Influence on Phase Behavior... 

Loden, 1995 Tokamura and Umekaga, 2005) as well as to study the efficacy and the cutaneous tolerance of cosmetics, such as shampoos, bath or shower gels, cleansing emulsions, make-up remover, etc. (Gloor et al, 2004 Bomkessel et al 2005). 

Removal of solids also decreases the stability of the hquid-liquid emulsion, making liquid-liquid separation easier. 

In many cases, emulsion specifications are stringent, and meeting them is a challenge that requires not only the guidelines found in industrial chemical recipes but also a full engineering treatment of the involved phenomena. The present chapter deals with the formulation engineering approach to emulsion making. 

In the second part of this chapter, basic operations of formulation engineering dedicated to emulsion making are proposed, using the formulation-composition framework discussed in the first part. 

We have shown that the current state of the art in emulsion science, particularly the formulation-composition mapping of emulsion properties, is general know-how that may he segregated into basic operations for the formulation engineering approach to emulsion making. 

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