Freeze drying is a specialized preservation method that was initially industrialized to preserve pharmaceuticals for battlefield applications. It is now broadly applied to enable the long-term stability of various fast-moving consumer goods, including medicines and food products. Traditional preservation methods involve dehydrating materials by gradually heating them to remove moisture, but this practice has a distinct lack of specificity. Nutrients and flavors can be removed from the material as a result, making it unsuitable for the preservation of composition-sensitive products.
This article will explore the freeze drying process in more detail:
Freeze Drying Procedure
There are several sensitive stages to freeze drying methodologies. Firstly, the material must be treated before being isolated in a freeze drying vacuum chamber. High purity solvents and gas species can be introduced to the material to enhance the end-product quality and optimize the drying procedure.
Secondly, the temperature of the sample is gradually decreased at pre-defined increments, either through consistent reduction or cycle gradients. Different applications require different techniques to achieve the critical low temperature at which a material’s solid, liquid and gas phases can coexist. Whether it is achieved through rapid freezing or annealing, this critical point allows for moisture desorption from the structure as ice.
The next stage involves drying the material at ultra-low pressures of just a few millibars and heating it to a precise degree to encourage sublimation, thus reducing the risk of moisture uptake. This part of the freeze drying process requires vacuum conditions to accelerate the phase transition of ice to water vapor. Liquid molecules are then removed from the adsorbent substrate of the material through a secondary drying process, which involves elevating the material’s temperature in conjunction with its adsorption isotherms. Typically, the pressure is further reduced to encourage a final stage of moisture desorption, before the vacuum conditions are flooded with inert gases.
Each of these processes is application and product specific, with multiple integral parameters for ensuring materials are correctly preserved.
Process Monitoring for Freeze Drying Equipment
Quadrupole analyzers are routinely used for process control of gas phase transition procedures. The HPR-30 gas analyzer, for example, is equipped to perform vacuum process control and leak detection with easy integration between a freeze drying condenser and chamber. It can detect the onset of secondary drying phase conditions with excellent degrees of automation, enabling improved repeatability of distinct procedures. This fully configurable system has a sensitive detection rate of 5 parts per billion, enabling highly precise sampling to support end-point detection.
By monitoring the sample chamber composition at distinct stages of the freeze drying process, researchers can acquire real-time information for sublimated water vapor and potential contaminants. The HPR-30 has been successfully used in production environments for on-line monitoring, and in research environments for cycle development, optimization, and validation.
Freeze Drying Solutions with Hiden Analytical
Hiden Analytical supplies an exceptional range of quadrupole mass spectrometers for a dynamic range of industrial and research applications. Our gas analyzers are equipped for process monitoring of integral processes for various sectors, including food and pharmaceuticals.