Encapsulation soluble materials

Advantages Major advantages of an encapsulation process involve the fact that waste materials never come into contact with water, therefore, soluble materials (such as sodium chloride) can be successfully surface-encapsulated. The impervious jacket also eliminates all leaching into contacting waters as long as the jacket remains intact. 

Hard fats are used to coat water-soluble bioactives. Release occurs by heating above the melting point of the fat or by mechanical rupture. Fat coatings have been used for protecting many water-soluble materials, which may otherwise be volatilized or damaged during thermal processing and to deliver materials such as ferrous sulfate, vitamins and other minerals. The peptides of casein hydrolysates encapsulated in lipospheres were shown to have reduced bitterness (Barbosa et al. 2004). 

G. B. Beestman, High Concentration Encapsulation of Water-Soluble Materials, United States Patent 4,534,783,1985. 

Liposomes are characterized by a lipid bilayer structure with clearly separated hydrophilic and hydrophobic regions. Hydrophilic portions of bilayer lipids are directed towards the internal and external aqueous phases, whereas hydrophobic portions of both lipid layers are directed towards each another, forming the internal core of the membrane. A useful feature of liposomes used for drug delivery is that they allow for localization and encapsulation both water-soluble and water-insoluble substances, either together or separately. Water-soluble materials are entrapped in... 

Both methods allow the subsequent coating of the granules [8J. By selecting appropriate coating materials one can design specific properties into the encapsulated flavourings. Apart from water-soluble materials, it is also possible to coat with fat. 

A promising application of the self-assembly of nanoparticles at droplet surfaces is the interfacial crosslinking of chemically functionalized nanoparticles. This enables the encapsulation of water-soluble or oil-soluble materials inside the resulting nanocontainers. By varying the concentration of reactive moieties, it will be possible to control the permeability and strength of these nanostructured membranes. 

Fig. 3 Miniemulsion polymerization process for the encapsulation of soluble materials...

Polymer coacervation can occur in either aqueous or organic liquids. Coacervation in aqueous liquids and the related processes are mainly used to encapsulate water-immiscible liquids or water-insoluble solid particles. On the other hand, coacervation in organic liquids, or sometimes called phase separation in organic liquids, is used to encapsulate core materials that are not miscible or soluble in the organic liquids. It may be induced by the addition of a nonsolvent to the polymer solution or by the addition of an incompatible polymer based on polymer-polymer incompatibility. This chapter will only discuss the coacervation in aqueous liquids. 

Two main coacervation techniques can be considered aqueous, which can only be used to encapsulate water-insoluble materials (hydrophobic core materials presented in solid or liquid state), and organic in which the organic phase permits the encapsulation of hydro-soluble material, requiring the utilization of organic solvents (Martins, 2012). 

Figure 4d represents in situ encapsulation processes (17,18), an example of which is presented in more detail in Figure 6 (18). The first step is to disperse a water-immiscible Hquid or soHd core material in an aqueous phase that contains urea, melamine, water-soluble urea—formaldehyde condensate, or water-soluble urea—melamine condensate. In many cases, the aqueous phase also contains a system modifier that enhances deposition of the aminoplast capsule sheU (18). This is an anionic polymer or copolymer (Fig. 6). SheU formation occurs once formaldehyde is added and the aqueous phase acidified, eg, pH 2—4.5. The system is heated for several hours at 40—60°C.

Solvent Evaporation. This encapsulation technology involves removing a volatile solvent from either an oil-in-water, oil-in-oil, or water-in-oH-in-water emulsion (19,20). In most cases, the shell material is dissolved in a volatile solvent such as methylene chloride or ethyl acetate. The active agent to be encapsulated is either dissolved, dispersed, or emulsified into this solution. Water-soluble core materials like hormonal polypeptides are dissolved in water that contains a thickening agent before dispersion in the volatile solvent phase that contains the shell material. This dispersed aqueous phase is gelled thermally to entrap the polypeptide in the dispersed aqueous phase before solvent evaporation occurs (21). 

Spray Drying. Spray-dry encapsulation processes (Fig. 7) consist of spraying an intimate mixture of core and shell material into a heated chamber where rapid desolvation occurs to thereby produce microcapsules (24,25). The first step in such processes is to form a concentrated solution of the carrier or shell material in the solvent from which spray drying is to be done. Any water- or solvent-soluble film-forming shell material can, in principle, be used. Water-soluble polymers such as gum arable, modified starch, and hydrolyzed gelatin are used most often. Solutions of these shell materials at 50 wt % soHds have sufficiently low viscosities that they stiU can be atomized without difficulty. It is not unusual to blend gum arable and modified starch with maltodextrins, sucrose, or sorbitol. 

Liquid food ingredients encapsulated are typically oil-soluble flavors, spices (see Flavors and spices), and vitamins (qv). Even food oils and fats are encapsulated (63). These core materials normally are encapsulated with a water-soluble shell material appHed by spray drying from water, but fat shell formulations are used occasionally. Preferred water-soluble shell materials are gum arabic, modified starch, or blends of these polymers with maltodextrins. Vitamins are encapsulated with 2ero bloom strength gelatin by spray drying. 

---