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Why is freeze-drying performed under low pressure?
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vacuum technology
Diagram of a McLeod gauge.
Freeze-drying is performed under high vacuum conditions to facilitate the sublimation of water from a frozen state directly into a gaseous state, bypassing the liquid phase.12
In the context of vacuum technology, this process is used to disturb the equilibrium conditions that exist at normal atmospheric pressure. By lowering the pressure, the system effectively removes volatile substancesāin this case, waterāfrom the bulk of the material. This method is essential for preservation, as it allows for the removal of moisture without the structural damage or chemical changes that might occur if the material were to melt into a liquid state.31