摘要：Many pharmaceutical and food products when they are in solution are susceptible to deactivation over a period of time. Such materials are freeze dried soon after their production in order to stabilize them and; therefore, they keep their bioactivity for a long time. In this study, first of all, the principle of freeze drying process was described. Next, the importance of freezing in the freeze drying was emphasized and the key points in a freeze drying operation were presented. Finally, first and second freezing stages that play important roles in freeze drying were examined.
