A third component essential in freeze-drying system is energy. Energy is essential in the form of heat. Almost ten times, much energy is required to sublime a gram of water from the frozen to the gaseous state as is required to freeze a gram of water, (2700 joules per gram of ice).
http://ijntps.org/File_Folder/0047.pdf
The term “lyophilization” describes a process to produce a product that “loves the dry state” [2]. PRINCIPLE The main principle involved in freeze drying is a phenomenon called sublimation, where water passes directly from solid state (ice) to the vapor state without passing through the liquid state.
http://ijntps.org/File_Folder/0047.pdf
Foreword This booklet has been developed to serve as a basicguide to the freeze drying process. The informationpresented is generic in nature and is the result ofresearch and experience by Labconco personnel andusers of freeze drying equipment.
http://www.nbtc.cornell.edu/sites/default/files/freeze_drying_guide.pdf
Appropriate scale-up of a freeze drying process in a cost effective and efficient manner involves smart use of experimental tools to monitor the drying process of product. It is hypothysed that cycles developed and/or used in the laboratory drier will correlate to cycles used in the production dryer [51].
http://ijntps.org/File_Folder/0047.pdf
Principles of Freeze Drying The freeze drying process consists of three stages:prefreezing, primary drying, and secondary drying.Prefreezing: Since freeze drying is a change in statefrom the solid phase to the gaseous phase, material to befreeze dried must first be adequately prefrozen.
http://www.nbtc.cornell.edu/sites/default/files/freeze_drying_guide.pdf
Most products are frozen well below their eutecticor glass transition point (Point A), and then thetemperature is raised to just below this criticaltemperature (Point B) and they are subjected to areduced pressure. At this point the freeze drying processis started.
http://www.nbtc.cornell.edu/sites/default/files/freeze_drying_guide.pdf
The product to be dried is frozen under atmospheric pressure. Then, in an initial drying phase referred to as primary drying, the water (in form of ice) is removed by sublimation; in the second phase, called secondary drying, it is removed by desorption. Freeze drying is carried out under vacuum [20].
http://ijntps.org/File_Folder/0047.pdf
One method isto apply heat directly through a thermal conductor shelfsuch as is used in tray drying. Another method is to useambient heat as in manifold drying. Secondary drying: After primary freeze drying iscomplete, and all ice has sublimed, bound moisture isstill present in the product.
http://www.nbtc.cornell.edu/sites/default/files/freeze_drying_guide.pdf
sucrose, the product temperature must remain below acritical collapse temperature during primary drying. Thecollapse temperature for sucrose is -32° C. No matter what type of freeze drying system is used,conditions must be created to encourage the free flow ofwater molecules from the product.
http://www.nbtc.cornell.edu/sites/default/files/freeze_drying_guide.pdf
A tray freeze-dryer is used to produce the driest product for long-term storage. A tray freezedryer allows the product to be frozen in place and performs both primary (unbound water removal) and secondary (bound water removal) freeze-drying, thus producing the driest possible end-product.
http://ijntps.org/File_Folder/0047.pdf
which mission was freeze drying first used
The Freeze Drying was first used in Apollo 7 Mission.