Freeze-drying monitoring via Pressure Rise Test: the role of pressure sensor dynamics

This paper is focused on the Pressure Rise Test method that is commonly used to monitor a freeze-drying cycle. Its performances seemed to be dependent on processing conditions and/or batch and equipment size. Here, we demonstrate that this behavior was linked to the response of the pressure sensor, which is commonly neglected by all the algorithms proposed in literature. An update of these algorithm, named DPE3+, is here proposed so as to solve this problem. The new algorithm was found to give accurate estimations of product temperature and drying time whichever is the size of the batch. This result can be generalized to different equipment sizes and more or less aggressive heating cycles.