Cultures of most bacteria may be preserved indefinitely by this means. The several methods in use employ usually phosphorus pentoxide as a dessicant, coupled with the use of a high vacuum pump to expedite evaporation. After primary drying the ampoules are connected to a manifold equipped with multiple exhaust lugs and the pump restarted. After due drying time the ampoules are checked with a high frequency vacuum tester, and sealed while the pump is still operating.
Method of tissue preparation in which a tissue specimen is frozen and then dehydrated at a low temperature under highvacuum conditions. In this process, the frozen water in material is sublimated directly from solid phase to gas.
Also known as lyophilisation. A method of drying in which the material is frozen and subjected to high vacuum. The ice sublimes off as water vapour without melting. Freeze-dried food is very porous, since it occupies the same volume as the original and so rehydrates rapidly. There is less loss of flavour and texture than with most other methods of drying. Controlled heat may be applied to the process without melting the frozen material; this is accelerated freeze drying.
A method of preserving food or tissue specimens by freezing rapidly and drying in a vacuum.
A method for the fixation of histological specimens, involving a minimum of chemical and physical change. Specimens are immersed in isopentane cooled to -190°C in liquid air. This fixes the tissue instantly, without the formation of large ice crystals (which would cause strurtural changes). The tissue is then dehydrated in a vacuum for about 72 hours at -32.5°C.
Preservation of tissue by rapidly freezing the specimen and then dehydrating it in a high vacuum.
A technique used in the preservation of plant tissues, microorganisms etc., whereby water is removed under vacuum while the tissue remains in the frozen state.