Traditional and Contemporary Drying Methods an Overview

The most crucial step in every pharmaceutical industry is drying. Drying forms one of the method that is frequently utilized to increase the product stability of biotherapeutics. Basically, drying can be done by two processes viz. natural drying and mechanical drying or artificial drying based on source of energy. Natural drying takes place under the influence of sunlight and wind and is of three types viz. sun, solar and shade drying. In natural drying there is no control over temperature, air flow and humidity whereas in artificial drying, these conditions are well controlled. In case of natural drying, it may be either direct sun-drying or in the shed. If the natural color of the drug (digitalis, clove, senna) and the volatile principles of the drug (peppermint) are to be retained, drying in shed is preferred. If the contents of the drugs are quite stable to the temperature and sunlight, the drugs can be dried directly in sunshine (gum acacia, seeds and fruits). Drying by artificial means includes drying the drugs in an oven; i.e., tray-dryers; vacuum dryers and spray dryers. The pharmaceutical industry uses a variety of drying systems, including fluidized bed drying, freeze-drying, microwave drying and spray drying. Many advantages result from removing water content through the drying process, such as lower transportation costs, easy handling and storage, and increased stability.