Freeze drying
Freeze drying
Freeze drying (pronounced: /friːz ˈdraɪ.ɪŋ/), also known as lyophilization or cryodesiccation, is a low temperature dehydration process that involves freezing the product, lowering pressure, then removing the ice by sublimation. This is in contrast to dehydration by most conventional methods that evaporate water using heat.
Etymology
The term "freeze drying" is a combination of the words "freeze", which comes from the Old English "freosan" meaning "to turn to ice", and "drying", which comes from the Old English "dryge" meaning "free from moisture". The term "lyophilization" comes from the Greek words "lyo" (to free or to dissolve) and "philos" (loving), indicating the process's ability to dry materials without causing much damage.
Process
Freeze drying is a three-step process. First, the material is frozen, usually in a laboratory freeze-drying machine that has a large chamber for the material and a freezing coil. The second step is primary drying (sublimation), where the pressure is lowered and heat is added to the material in order for the water in the material to sublimate. The third step is secondary drying (adsorption), where the freeze-dried material is heated to a higher temperature to remove any water molecules that are still present in the material.
Applications
Freeze drying is used in a variety of sectors, but it is particularly important in the pharmaceutical industry, where it is used to increase the shelf life of products, such as vaccines and other injectables. By removing the water from the material and sealing the material in a vial, the product can be easily stored, shipped, and later reconstituted to its original form with the addition of water. It is also used in the food industry to preserve food, in taxidermy to preserve specimens, and in ceramics to prepare clay.
Related terms
- Sublimation (phase transition): The transition of a substance directly from the solid to the gas state, without passing through the liquid state.
- Dehydration: The process of removing water or moisture from a substance or object.
- Pharmaceutical industry: The commercial industry that discovers, develops, produces, and markets drugs or pharmaceutical drugs for use as medications.
- Vaccine: A biological preparation that provides active acquired immunity to a particular infectious disease.
External links
- Medical encyclopedia article on Freeze drying
- Wikipedia's article - Freeze drying
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