Product, dried reconstitution

Each interferon preparation was ultracentrifuged at 20,000 revolutions per minute for one hour to remove tissue debris and inactivated virus. The supernatant was dialyzed against distilled water (1 400) for 24 hours at4°C. The material was then freeze-dried. The dried product was reconstituted in one-tenth of the original volume in distilled water and dispensed into ampoules. Reconstituted solutions were assayed for interferon activity, examined for toxicity, and tested for sterility. 

Rodrfguez-Hernandez, G.R. et al.. Spray-drying of cactus pear juice (Opuntia strep-tacantha) effect on the physicochemical properties of powder and reconstituted product, Drying TechnoL, 23, 955, 2005. 

While liquid milk is little used in biscuit manufacture for practical reasons to do with lack of stability, skimmed milk solids are used. The preferred ingredient is skimmed milk powder. This is normally dispersed in twice its own weight of water to ensure that it is evenly dispersed in the finished product. The reconstituted milk powder has the same keeping properties as liquid milk so it must be refrigerated. Merely dry blending the milk powder is likely to produce a finished product with small brown specks of caramelised milk powder in it. 

Providing the product is reconstituted in a small volume of diluent, the resulting solution is more concentrated than the formulated solution before freeze-drying. It is therefore easier to assay minute amounts of drug or impurities and the analytical methods used for QC release can be implemented. 

Based on these studies in microstructure and the mechanism of moisture removal on dehydration and moisture absorption during reconstitution, good quality dehydrated products which reconstitute well upon dehydration should have the following characteristics cells must not be totally collapsed, cell walls must remain intact and intercellular spaces must be maintained in the dried product. The latter will allow capillary action to draw the water into the vicinity of the cells during the process of rehydration. Water can then diffuse across the intact cell wall and into the cells to reestablish turgor. 

So far, in all examples the method for agglomeration was based on the use of low-density gas fluidized beds. As discussed in Chapter 5 and in much more detail in earlier publications [B.48, B.93, B.97], adhesion by coalescence of irregularly moving particles in low-density fluidized beds yields relatively small, structurally loose, and low-strength agglomerates, which (if reconstitution in liquids is desired) exhibit instant characteristics. In most cases these processes operate continuously, but batch operations for very sensitive materials (vitamins) are also possible. Fig. 6.4.1-16 shows as examples the photomicrographs of two typical products (dry milk and coffee extract). 

Although the shelf-life of a labile bioproduct will be appreciably extended by freeze-drying, stored material will not be immune to thermal decay and it may be necessary to store the freeze-dried product within a refrigerator to ensure maximum stability. For use, the dried product is reconstituted with water or an alternative medium and the hazards associated with both product storage and reconstitution will be addressed in section 10.4. 

Agglomeration. The process of treating dried products, particularly nonfat products, ia order to iacrease speed and abHity to reconstitute those products, is known as instantizing or agglomeration. Particles are agglomerated iato larger particles which dissolve more easHy than smaH particles. In... 

Lyophilization. LyophiLization is essentially a drying technology. Some dmgs and biologicals are thermolabile and/or unstable in aqueous solution. Utilization of freeze drying permits the production of granules or powders that can be reconstituted by the addition of water, buffered solution, or mixed hydrophilic solvents just prior to use, eg, certain antibiotic suspensions. 

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. 

Some parenteral dragp are available as a crystal or a powder. Because these dru have a short life in liquid form, they are available in ampules or vials in dry form and must be made a liquid (reconstituted) before they are removed and administered. Some of these products have directions for reconstitution on the label or on the enclosed package insert. The manufacturer may give... 

Instant tea produced as described above will dissolve completely in hot water but not in cold water, as the caffeine-polyphenol complexes are insoluble under those conditions. Since virtually all instant tea manufacture in the U.S. is for iced tea preparation, process modification is required. This initial extract may be cooled to 5 to 10°C and the cold water insoluble material or cream be allowed to precipitate. Under these conditions, 20 to 35% of the extract solids may be separated by centrifugation. The supernatant solids will reconstitute in cold water after concentration and drying.105 It is also possible to process the cream to make a portion of it compatible with the product and thereby retain the caffeine and some polyphenolic components that are present in this fraction.106 Commercial use of the enzyme Tannase, which removes gallic acid from gallated tea polyphenols107 and reduces cream formation108 can be used to reduce cream losses and manufacture instant teas retaining more of the natural polyphenol content. 

Dry powders for reconstitution as an injectable product may be produced by several methods filling the product into vials as a liquid and freeze-drying, aseptic crystallization followed by powder filling, and spray-drying followed by powder filling. A brief discussion of each follows. 

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