Storage freeze dried materials

Frozen materials should be stored at —20°C, fruits and salad vegetables at around 4°C, and canned foods at room temperature. Powdered and freeze-dried materials should be stored in the dark in their original containers. Storage of fresh materials should preferably not exceed 3 days. After the initial preparation (see below), fresh or cooked materials can be conveniently stored at -20°C for a short time prior to extraction. 

By nature, freeze-dried produets are hygroscopic, so exposure to moisture during storage can destabilize them. Packaging used for freeze-dried materials must be impermeable... 

A freeze-dried material undergoes fewer adverse changes than those preserved by pickling, salting, canning, or normal heat dehydration. The product requires simpler storage and transportation systems, and if sealed under vacuum or an inert gas, usually retains most of its biological and physical characteristics indefinitely. 

Biological standards and reference materials are stored at the appropriate temperature in controlled, calibrated, monitored, and alarmed storage facilities. The freeze-dried materials are normally stored at —20°C to maintain stability over the period of the materials availability, which may be a decade or more. Freeze-dried materials should be sufficiently stable to withstand short-term shipping at ambient temperatures without deterioration to their intended use. 

Biological standards and reference materials are supplied for immediate use and prior to use should be stored at the temperature indicated on the label. Once freeze-dried material is reconstituted, users must determine the stability of the material according to their own methods of preparation, storage, and use. In general, NIBSC follows the WHO policy in not setting expiry dates for freeze-dried biological standards and reference materials. 

Fig. 7 Collapse is characteristic of amorphous materials, and can occur either during the freeze-dry process or during storage. 

Freeze-drying for preparation and storage of standards has found especially widespread application in the clinical field, particularly in relation to material standards containing a large variety of analytes. 

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