Emulsions spray drying

Giunchedi P, Gavini E, Bonacucina G, Palmieri GF. Tabletted polylactide microspheres prepared by a w/o emulsion-spray drying method. J Microencapsul 2000 17(6) 711-720. 

Aroma Carriers Emulsifiers Feed/Emulsion Spray-Drying Air ... 

Compounded Flavors. Liquid or dry blends of natural or synthetic flavor compounds are called compounded flavors. Most commercial preparations are available as water- and oil-soluble Hquids, spray-dried and plated powders, emulsions, and carbohydrate-, protein-, and fat-based pastes. Compounded flavors are used throughout the food industry in confections, baked goods, snack foods, carbonated beverages, and processed foods (53). 

The second step is to disperse the core material being encapsulated in the solution of shell material. The core material usually is a hydrophobic or water-knmiscible oil, although soHd powders have been encapsulated. A suitable emulsifier is used to aid formation of the dispersion or emulsion. In the case of oil core materials, the oil phase is typically reduced to a drop size of 1—3 p.m. Once a suitable dispersion or emulsion has been prepared, it is sprayed into a heated chamber. The small droplets produced have a high surface area and are rapidly converted by desolvation in the chamber to a fine powder. Residence time in the spray-drying chamber is 30 s or less. Inlet and outlet air temperatures are important process parameters as is relative humidity of the inlet air stream. 

Because of the multiple conjugated olefinic stmcture in the molecule, pure crystalline carotenoids are very sensitive to light and air and must be stored in sealed containers under vacuum or inert gas to prevent degradation. Thus, commercial utilization as food colorings was initially limited however, stable forms were developed and marketed as emulsions, oil solutions and suspensions, and spray-dried forms. 

Poly(vinyl acetate) and its copolymers with ethylene are available as spray-dried emulsion soHds with average particle sizes of 2—20 p.m the product can be reconstituted to an emulsion by addition of water or it can be added directly to formulations, eg, concrete. The powders may be used to raise soHds of a lower soHds latex. Solutions of resin in methyl and ethyl alcohol at 2—50 wt % soHds are also available. 

In contrast to other polymers the resistance to water permeation is low due to the hydrolysis of the poly(vinyl acetate) (163,164). Ethylene copolymers have been developed which have improved water resistance and waterproofness. The polymer can be used in the latex form or in a spray-dried form which can be preblended in with the cement (qv) in the proper proportion. The compressive and tensile strength of concrete is improved by addition of PVAc emulsions to the water before mixing. A polymer-soHds-to-total-soHds ratio of ca 10 90 is best. The emulsions also aid adhesion between new and old concrete when patching or resurfacing. 

Since the 1940s, alkanesulfonates have served as emulsifiers in the emulsion polymerization of vinylchloride. Nevertheless, the detailed mechanisms of this process are not yet completely known. An important advantage of using alkanesulfonates is that they produce latices with a high solid content, which can be effectively processed by spray drying [90]. 

The emulsion technique is convenient when the drug is particularly sensitive to certain parameters connected to the spray-drying. The emulsion technique may be associated to cross-Unking or other treatments of the microspheres. The following examples are self-explanatory. 

Gum acacia is a unique polysaccharide, with some peptides as part of the structure and has a range of different uses. It was originally the gum in gum sweets although some gum sweets do contain modified starch as a substitute. The replacement of gum is not because the substitute performs better but because there have been supply problems with gum acacia. Gum acacia is likely to be encountered in bakeries in small quantities when it has been used to make emulsions of citrus oils as a bakery flavour. It is possible to use gum acacia in making dry flavours from oils such as citrus by making an emulsion and then spray drying it. 

A very recent development is encapsulation of actives in colloidosomes [16, 41]. The method is analogous to liposome entrapment. Selectively permeable capsules are formed by surface-tension-driven deposition of solid colloidal particles onto the surface of an inner phase or active ingredient in a water-in-oil or an oil-in-water emulsion composed of colloidal particles. Initially synthetic polymer microparticles were used but more recently a natural alternative has been described based on small starch particles. After spray-drying, redispersible emulsions can be formed. 

The polymer in emulsion polymerization is isolated by either coagulating or spray drying. 

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