Drying of Products,Enzymes,Spray Drying,Vacuum Drying,Freeze Drying,Plasma Fractions

www.molecular-plant-biotechnology.info

	Drying of Products - Drying makes the products suitable for handling and storage. It should be accomplished with a minimum rise in temperature due to heat sensitivity of most products. Addition of sugars or other stabilizers improves the heat tolerance of some products like enzymes and pharmaceutical preparations. The most common approaches to drying are as follows: (i) vacuum drying, (ii) spray drying, and (iii) freeze drying.
In spray drying, the solution or slurry to be dried is atomized by a nozzle or a rotating disc. A current of hot (l50-250°C) air is passed; the drying is so rapid that the temperature of particles remains very low. Spray drying is used for enzymes, antibiotics and food products. Vacuum drying uses both heat and vacuum for drying; it can be applied both in batch mode (e.g., chamber dryers) and in continuous mode (e.g., rotating drum vacuum dryers). In freeze drying, the liquor to be dried is first frozen and the water is sublimed from the frozen mass. A very low pressure (partial vacuum) is maintained to promote sublimation of water. The energy needed for; sublimation is provided by heated plates and radiation on to the surface. The temperature of solid is regulated by regulating the pressure in the drying chamber: This is the gentlest method of drying, and is used for many pharmaceutical products, e.g., viruses, vaccines, plasma fractions, enzymes, etc., and in food industries.