chapter  11
18 Pages


As the efficiency of refrigeration systems increased, and powerful re­ frigerants were introduced that were capable of generating tempera­ tures as low as -90° C within the freeze dryer, the freeze drying community enjoyed a period where the performance of the freeze dryer was taken for granted. It is unfortunate that many cycles are de­ veloped with a freezing step that is dictated, not by the solidification temperature of the product, but by the ultimate shelf minimum tem­ perature of the development freeze dryer. Once a cycle is described in a product licence it becomes difficult to change, even though equiva­ lent results could be obtained at higher temperatures with a smaller energy consumption.