Freeze-drying causes less damage to the substance than other
dehydration methods using higher temperatures. Nutrient factors that are sensitive to heat are lost less in the process as compared to the processes incorporating heat treatment for drying purposes. biologics, and other injectables. By removing the water from the material and sealing the material in a glass vial, the material can be easily stored, shipped, and later reconstituted to its original form for injection. Another example from the pharmaceutical industry is the use of freeze drying to produce tablets or wafers, the advantage of which is less
excipient as well as a rapidly absorbed and easily administered dosage form. Freeze-dried pharmaceutical products are produced as lyophilized powders for reconstitution in vials, and more recently in prefilled syringes for self-administration by a person. Examples of lyophilized pharmaceutical drugs include: •
Vancomycin, an intravenous
antibiotic for treatment of complicated skin infections,
bloodstream infections,
endocarditis, bone and joint infections, and
meningitis. •
Activase, an intravenous "
blood clot buster" used for treatment of
ischemic stroke. •
Carmustine, a
chemotherapy drug used for treatment of
glioblastoma, brainstem glioma, and other brain tumors.
Biological products Examples of lyophilized biological products include: • Many vaccines such as live measles virus vaccine, typhoid vaccine, and meningococcal polysaccharide vaccine groups A and C combined. • This also include antibodies, some of which are blockbuster drugs:
etanercept (
Enbrel by
Amgen),
infliximab (Remicade by
Janssen Biotech),
rituximab, and
trastuzumab (Herceptin by
Genentech). • Cell extracts that support cell-free biotechnology applications such as point-of-care diagnostics and biomanufacturing are also freeze-dried to improve stability under room temperature storage. Lyophilized biologics can be pressed into pellets and tablets for
anhydrous and high-density, solid-state storage of biological products. In bioseparations, freeze-drying can be used also as a late-stage purification procedure, because it can effectively remove solvents. Furthermore, it is capable of concentrating substances with low
molecular weights that are too small to be removed by a
filtration membrane. Freeze-drying is a relatively expensive process. The equipment is about three times as expensive as the equipment used for other separation processes, and the high energy demands lead to high energy costs. Furthermore, freeze-drying also has a long process time, because the addition of too much heat to the material can cause melting or structural deformations. Therefore, freeze-drying is often reserved for materials that are heat-sensitive, such as
proteins,
enzymes,
microorganisms, and
blood plasma. The low
operating temperature of the process leads to minimal damage of these heat-sensitive products.
Live material Some live cell cultures can be freeze-dried, stored for an extended period, and then reconstituted into a live, functional state. An excipient, more specifically a
cryoprotectant, may be required. • Prokaryotes and yeast are relatively easy to freeze-dry and then resuscitate. • Live vaccines (described above) are also examples of this class. • The simpler blood cells (red blood cells and platelets) have been freeze-dried. With the right protection, recovery rates are as high as 90%. Even if the cell is damaged beyond resuscitation, it is preserved. This can be helpful for later research too: although the type strain culture for
Vampirovibrio chlorellavorus could not been resuscitated, it contained enough DNA for its genome to be sequenced.
Technological industry In
chemical synthesis, products are often freeze-dried to make them more stable, or easier to
dissolve in
water for subsequent use. In
nanotechnology, freeze-drying is used for nanotube purification to avoid aggregation due to capillary forces during regular thermal vaporization drying.
Food bars ,
melon,
meatball soup,
tarator The primary purpose of freeze drying within the food industry is to extend the shelf-life of the food while maintaining the quality. It can also preserve raw ingredients such as
egg whites for baking.
NASA and military rations Because of its light weight per volume of reconstituted food, freeze-dried products are popular and convenient for
hikers, as military rations, or astronaut meals. An
instant coffee can be produced by freeze-drying a water extract of roasted beans.
Insects Freeze-drying is used extensively to preserve insects for the purposes of consumption. Whole freeze-dried insects are sold as
exotic pet food, bird feed, fish bait, and increasingly for
human consumption. Powdered freeze-dried insects are used as a
protein base in animal feeds, and in some markets, as a
nutritional supplement for human use. Freeze-drying is also used as a means to memorialize pets after death. Rather than opting for a
traditional skin mount when choosing to preserve their pet via taxidermy, many owners opt for freeze-drying because it is less invasive upon the pet's body.
Other uses Organizations such as the Document Conservation Laboratory at the United States
National Archives and Records Administration (NARA) have done studies on freeze-drying as a recovery method of water-damaged books and documents. While recovery is possible, restoration quality depends on the material of the documents. If a document is made of a variety of materials, which have different absorption properties, expansion will occur at a non-uniform rate, which could lead to deformations. Water can also cause mold to grow or make inks bleed. In these cases, freeze-drying may not be an effective restoration method. Advanced
ceramics processes sometimes use freeze-drying to create a formable powder from a sprayed
slurry mist. Freeze-drying creates softer particles with a more homogeneous chemical composition than traditional hot
spray drying, but it is also more expensive. == Advantages ==