| Abstrakt | | The main steps during freeze-drying are outlined on the physico-chemical background of freezing and sublimation of water and aqueous solutions. In particular, the influence of dissolved substances on formation of eutectic mixtures and glasses is described as well as patheweys to obtain optimal ice structures for the drying process, including the application of cryoprotective substances. Drying by sublimation requires a high energy supply at low pressure in the drying chamber. Techniques which allow high drying rates are explained and methods are mentioned for the control of both freezing and drying. Secondary drying at higher temperatures is necessary, if strongly bound water has to be removed from the products.
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