Spray-Drying Techniques

One of the most widely used spray-drying techniques for coffee extract involves spraying percolated coffee extract at 40°F into the top of a baffled tower of hot air at 480°F initially. The cooler wet air is removed toward the bottom of the tower and finally a powder of the coffee extract solids leaves the tower at about 90°F. These solids are in the form of hollow beads and contain 3% moisture. 

The most common method to simultaneously dry and encapsulate flavours is the spray-drying technique (Fig. 21.11). For this technology, carrier materials like maltodextrin, starch and gum arabic are dissolved in water. As a next step, the liquid flavour raw material is emulsified in this slurry. Also non-volatile flavour components can be added. The slurry is atomised and dried in a spraydrying facility. 

Baras, B., Benoit, M., Poulain-Codefroy, O., Schacht, A., Capron, A., Cillard, J. and Riveau, G. (2000) Vaccine properties of antigens entrapped in microparticles produced by spray-drying technique and using various polyester polymers. Vaccine 18, 1495-1505. 

A recent application of particle formation by solvent evaporation and spray-drying techniques is based on the concept of the aerodynamic diameter. According to Eq. (8.5), the aerodynamic diameter dAer is correlated with the true particle diameter dP and the particle density pp° 5. It is evident that particles formed in a particle-formation process can be much bigger, provided that their density is very small. Increased bioavailability of such large porous insulin particles (Fig. 8.14) has been demonstrated on inhalation by rats and has been correlated with a... 

Bittner, B., Mader, K., et al. Tetracycline-HCl-loaded poly(DL-lactide-co-glycolide) microspheres prepared by a spray drying technique influence of gamma-irradiation on radical formation and polymer degradation. J. Contr. Rel. 59(1) 23—32, 1999. 

Pulmospheres are produced using a proprietary spray drying technique, with phosphatidylcholine as an excipient to produce hollow and porous particles with... 

In order to overcome the poor flowability and low compressibility of NaHCOs, a spray-drying technique... 

Kawashima, Y. Lin, S.Y. Ueda, M. Takenaka, H. Preparation of solid particulates of amino-pyrine-barbital complexes (pyrabital) without autooxidation by a spray drying technique. Drug Dev. Ind. Pharm. 1983, 9, 285-302. 

An interesting alternative approach to suspension formulations in HFA propellants is via engineered drug substance particles. Porous drug substance/ excipient particles can be produced via spray drying techniques. It is theoretically possible to match the density of the particles with that of the liquid propellant to produce a formulation with desirable suspension characteristics. ... 

Takada, S. Uda, Y. Toguchi, H. Ogawa, Y. Application of a spray drying technique in the production of TRH-containing injectable sustained-release microparticles of biodegradable polymers. PDA J. Pharm. Sci. Technol. 1995, 49 (4), 180-184. 

Lin, S. Kao, Y. Solid particulates of drug-Jl-cyclodextrin inclusion complexes directly prepared by a spray-drying technique. Int. J. Pharm. 1989, 56, 249-259. 

Takenaka H, Kawashima Y, Lin SY. Preparation of enteric-coated microcapsules for tableting by spray-drying technique and in vitro simulation of drug release from the tablet in GI tract. ] Pharm Sci 1980 69 1388-1392. 

Chen RC, Takahashi H. Okamoto H, Danjo K. Particle design of three-component system for sustained release using a 4-fluid nozzle spray-drying technique. Chem Pharm Bull 2006 54 1486-90. 

Chauhan B, Shimpt S, Paradkar A. Preparation and characterization of etoricoxib solid dispersions using lipid carriers by spray drying technique. AAPS niarm Sci Tech 2005 6 E405-B412. 

Komblum SS. Sustained-action tablets prepared by employing a spray-drying technique for granulation. J Pharm Sci 1968 58 125-7. 

In an extension of the spray-drying technique called spray roasting , evaporative decomposition of solutions (EDS) , spray pyrolysis , or aerosol pyrolysis , the temperature of the heated chamber is high enough to decompose the dried salts after the solvent has evaporated. Nitrate salts are used because of their low decomposition temperatures. The technique eliminates the problems of handling dried nitrate powders, which can be hydroscopic. These methods are used to prepare chalcogenide powders" and barium titanate . 

Spray dried flavourings have satisfied the demands of the food industry for quite some time. However, manufacturing technologies and application forms for food continue to develop. Modem flavourings have to keep up with these changes and with other special requirements put forward by producers. This has resulted in some further developments in the manufacture of encapsulated flavourings - the so-called complementary procedures - which have come into use in recent years. Complementary procedures are refinements, later developments of the spray drying technique. These methods are dealt with later in this section [1-3],... 

Fluticasone propionate, a steroidal drug, is known to exist in two polymorphic forms, namely, forms I and II. Form I can be readily obtained by crystallization from a variety of solvents. Standard spray-drying techniques can afford only form I. Form II, obtainable only by SFC, has a PXRD pattern completely different from that of form I (32,33). The relative amounts of forms I and II produced can be controlled by using different drug solvents. For example, form I is obtainable from pure acetonitrile while form II can be crystallized from pure methanol. The use of either acetone or ethyl acetate will yield a mixture of forms I and II. 

Other studies have included the formation of complexes using spray-drying techniques, including the preparation of cyclodextrin complexes. DSC may be used to determine the extent of drug inclusion within the cyclodextrin ring system, again via monitoring of the decrease in the heat of fusion (97). 

Sankarikntty B, Sreeknmar MM, Narayanan CS, Mathew AG. 1988. Studies on microen-capsulation of cardamon oil by spray drying technique. Journal of Food Science and Technology 25(6) 352-356. 

To achieve homogeneity with these relatively solublecompounds, which, however, have different solubilities, the mixed formates must be prepared by a special spray-drying technique [31]. The mixed oxalates, which are precipitated with oxalic acid and ammonium oxalate rather than with alkali oxalates (this tends to give more active catalysts), yield, as a rule, homogeneous materials via a simple precipitation. Complex oxalates are just as usable as the mixed oxalates [33]. 

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