Freeze dried - Definition and Overview

Freeze drying (also known as Lyophilization) is a dehydration process typically used to preserve a perishable material, or to make the material more convenient for transport. Freeze drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to gas. The greatly reduced water content that results inhibits the action of microorganisms and enzymes that would normally spoil or degrade the substance.

If a freeze-dried substance is sealed to prevent the reabsorption of moisture, the substance may be protected against spoilage for many years. Freeze drying tends to damage the tissue being dehydrated less than other dehydration methods, which involve higher temperatures.

The process has been popularized in the form of freeze dried ice cream and as an example of astronaut food. It is also popular and convenient for hikers because the reduced weight allows them to carry more food and reconstitute it with available water. Freeze drying is used in the manufacture of instant coffee as well as some pharmaceuticals.

External links

• http://home.howstuffworks.com/freeze-drying.htm/printable
• http://inventors.about.com/library/inventors/blfrdrfood.htm
• http://www.fda.gov/ora/inspect_ref/igs/lyophi.html
• http://www.rpi.edu/dept/chem-eng/Biotech-Environ/LYO/index.html

See also

• Food preservation