Working: steps involved in freeze drying are
1. Pre-treatment: Solution is concentrated in normal vacuum tray dryer before introducing in the chamber this reduces drying by 8-10 times.
2. Pre-freezing: Ampoules, vials and bottles having aqueous solution are packed and frozen in cold shelves at a temp. below - 500C.
3. Primary drying: The material to be dried is spread to increase the surface area for sublimation.98-99% moisture removed.
4. Secondary drying: Remaining moisture is removed by vacuum drying done at 50- 600C.It takes 10-20 hrs.
5. Packing: Packaging of product is performed carefully to protect it from moisture.
The containers should be closed under aseptic conditions.
Containers are labeled and packed in card-board boxes.after drying.