Food industry multiple emulsions

Several industrial systems involve emulsions, of which the following are worthy of mention. Food emulsions include mayonnaise, salad creams, deserts, and beverages, while personal care and cosmetics emulsions include hand creams, lotions, hair sprays, and sunscreens. Agrochemical emulsions include self-emulsifiable oils that produce emulsions on dilution with water, emulsion concentrates with water as the continuous phase, and crop oil sprays. Pharmaceutical emulsions include anaesthetics (O/W emulsions), hpid emulsions, and double and multiple emulsions, while paints may involve emulsions of alkyd resins and latex. Some dry-cleaning formulations may contain water droplets emulsified in the dry cleaning oil that is necessary to remove soils and clays, while bitumen emulsions are prepared stable in their containers but coalesce to form a uniform fihn of bitumen when apphed with road chippings. In the oil industry, many crude oils (e.g.. North sea oil) contain water droplets that must be removed by coalescence followed by separation. In oil slick dispersion, the oil spilled from tankers must be emulsified and then separated, while the emulsification of waste oils is an important process for pollution control. 

Another type of emulsion that has gained interest in food applications is the so-called multiple emulsion, which is basically an emulsion contained in a droplet. For example, a water-in-oil-in-water (W/O/W) emulsion means a multiple emulsion of water droplets inside an oil droplet that is dispersed in a continuous water phase. Recently, potential industrial applications in encapsulating active food components were recognized. One of the main difficulties in applying multiple emulsions is their low stability, which limits the applicability when prolonged stability and release are necessary (Muschiolik, 2007). Figure 32.16 shows a schematic representation of a W/O/W emulsion. 

Multiple emulsions usually refer to series of complex two-phase systems that result from dispersing an emul sion into its dispersed phase. Such systems are often referred to as water-in-oil-in-water (W/OAV) or oil-in-water-in-oil (O/W/0) emulsions, depending on the type of internal, intermediate, and continuous phase. Multiple emulsions were early recognized as promising systems for many industrial applications, such as in the process of immobilization of proteins in the inner aqu eous phase (37) and as liquid membrane systems in extraction processes (38). W/O/W emulsions have been discussed in a number of technical applications, e.g., as prolonged drug-delivery systems (39-44), in the context of controlled-release formulations (45), and in pharmaceutical, cosmetic, and food (46) applications. 

It is possible to take advantage of this great variety of parameters and control the release from the internal phase by one of these mechanisms, in developing applications of multiple emulsions for pharmaceuticals, cosmetics, and the food industries. 

The development of LbL assembly for use in food industry mainly involves oil droplets that are coated with multilayered interfaces, leading to (1) improved stability of oil-in-water emulsions, (2) controlled/triggered release of materials either in the core or in the multilayered shell, and (3) hollow capsules as carriers for active ingredients. For example, oil emulsions coated with multilayered sodium dodecyl sulfate (SDS)-chit-osan-pectin showed significantly improved stability against multiple freeze-thaw cydes. Also, multilayer-protected emulsions display better stability against lipid oxidation. However, all these examples are still in the devdopment phase, with continuing efforts to put in practical use. 

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