The material can be packaged in vacuum packed pouches or under a nitrogen gas atmosphere to prevent oxidation and resulting contamination and spoiling of the product. Pharmaceuticals are often freeze dried in vials fitted with a slotted stopper. The stopper is above the vial (also called ampoule) so that water can excape through the slot. When dry but still under vacuum, a mechanical lever system brings the trays together to push the stoppers down tightly. After removal from the dryer, metal caps are crimped over the flexible stoppers to insure the seal.
Much later, reconstitution is the next step. When the need for the specimen arises, simple addition of water will result in a refilling of the interstitial spaces in the porous dehydrated specimen. A small amount of time should be allowed for complete rearrangement and positioning of molecules and bonds. Special bonds, such as hydrogen bonding, sometimes need extra time to position and form. If all the bonds do not form properly, some characteristic of the specimen will be incorrect. Most food specimens can be stored dried for an infinite period of time, although a date for use will be recommended. Other specimens such as blood have a definite shelf life that may not be very long, but compared to their regular shelf life is quite an increase.
