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Duplex emulsions

In principle, an emulsion contained within an emulsion droplet, as shown schematically in Figure 7.24, can be regarded as an excellent reservoir for "active matter . Benichou et al. (2004) have suggested that complexes of proteins with polysaccharides can be employed to improve the steric stabilization of such a double ("duplex ) emulsion by forming a thick... [Pg.285]

In some oases, duplex emulsions are important. These are emulsions in emulsions. One can have water droplets in an oil phase, of which larger droplets have been made in a second aqueous phase this is called a water-in-oil-in-water duplex emulsion (W/O/W). Of course, one can also have the reverse (O/W/O emulsion). W/O/W are used in some medical applications (encapsulation of drugs), and in foods, to enhance the perception of fat, for example, but also to mask taste, for example, the taste of bitter peptides. One can also imagine that an O/W emulsion in which the oil phase is for the most part replaced by water droplets inside the oil phase, would combine some of the properties of a concentrated O/W emulsion with a much lower actual oil content of the product, with obvious advantages in terms of health. [Pg.306]

Several types of double emulsions have been documented. Some consist of a single, internal compartment while others have many internal droplets and are known as multiple-compartment emulsions. A schematic presentation of some double emulsions is shown in Fig. 1. The most common double emulsions are of W/O/W, but in some specific applications O/W/0 emulsions can also be prepared. The term multiple emulsion was coined historically because microscopically it appeared that a number (multiple) of phases were dispersed one into the others. In most eases it was proven that in practice most systems are composed of double (or duplex) emulsions. A more suitable and more accurate term for such systems should be, therefore, emulsified emulsions. ... [Pg.377]

Few fonnulations based on double emulsions (in which droplets of the dispersed phase further contain smaller dispersed droplets) are on the market as these consist of large, polydispersed droplets (10-100 (xm) that are thermodynamically unstable. ControUmg the release of compounds incorporated in double emulsions is normally achieved by stabilizing the interface of the inner emulsion, careful composition of the oil and aqueous phases, and/or stabilization of the secondary interface (Davis et al, 1985 Garti, 1997). However, most double emulsions tend to release entrapped compounds in an uncontrolled manner. A novel possibility for the stabilization of the inner emulsion is to use microemulsions. Pilman and co-workers (1980) reported the use of microemulsions dispersed within the inner phase of water-in-oil-in-water (w/o/w) duplex emulsions, and stabilized in a sodium caseinate solution resulting in emulsified microemulsions. In principle, these emulsified microemulsions may be used as controlled delivery system for nutraceuticals and pharmaceuticals. [Pg.159]

One may rationalize emulsion type in terms of interfacial tensions. Bancroft [20] and later Clowes [21] proposed that the interfacial film of emulsion-stabilizing surfactant be regarded as duplex in nature, so that an inner and an outer interfacial tension could be discussed. On this basis, the type of emulsion formed (W/O vs. O/W) should be such that the inner surface is the one of higher surface tension. Thus sodium and other alkali metal soaps tend to stabilize O/W emulsions, and the explanation would be that, being more water- than oil-soluble, the film-water interfacial tension should be lower than the film-oil one. Conversely, with the relatively more oil-soluble metal soaps, the reverse should be true, and they should stabilize W/O emulsions, as in fact they do. An alternative statement, known as Bancroft s rule, is that the external phase will be that in which the emulsifying agent is the more soluble [20]. A related approach is discussed in Section XIV-5. [Pg.504]

Emulsion binders for mineral coated stock enable good colour and printing properties Emulsions are used in all front coating operations, as well as duplexing and pre-pasting adhesives... [Pg.225]


See other pages where Duplex emulsions is mentioned: [Pg.333]    [Pg.333]    [Pg.463]    [Pg.1]    [Pg.103]   
See also in sourсe #XX -- [ Pg.306 ]




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