Freeze drying principle

Freeze drying refers to the process of removing moisture or other solvents from frozen biological products by sublimation. Sublimation refers to the process of solvents, such as water, like dry ice, which change from a solid to a gaseous state without going through a liquid state. The product obtained by freeze drying is called a lyophilizer, and the process is called lyophilization.

Why choose freeze drying:
Traditional drying can cause the material to shrink and damage the cells. The structure of the sample is not destroyed during the freeze drying process because the solid component is supported by the firm ice at its location. When the ice sublimes, it leaves pores in the dry remaining material. This preserves the biological and chemical structure of the product and the integrity of its activity.
In the laboratory, lyophilization has many different uses and is indispensable in many biochemical and pharmaceutical applications. It is used to obtain biological materials that can be preserved for a long period of time, such as microbial culture, enzymes, blood, and pharmaceuticals, in addition to the long-term preservation stability, retaining its inherent biological activity and structure. To this end, lyophilization is used to prepare tissue samples for structural studies (eg, electron microscopy studies). Freeze drying is also used in chemical analysis to obtain dried samples or to concentrate samples to increase analytical sensitivity. Freeze-drying stabilizes the sample composition without changing the chemical composition, which is an ideal analytical aid.
Freeze drying implementation:
Freeze drying can occur naturally. In the natural case, this process is slow and unpredictable. Through the freeze-drying system, people have improved and subdivided many steps to speed up the process.
Freeze drying system:
A basic freeze-drying system consists of: • a drying chamber or manifold; an evacuation system to overcome obstacles and accelerate gas flow • a heat source to provide energy • a cryogenic condenser to maximize and capture vapor pressure difference Vapor freezes it to avoid water vapor pollution
Freeze-drying steps:
The freeze-drying process consists of three steps: • Pre-freezing to prepare samples for the subsequent sublimation process. · Primary drying, in which the ice sublimes without melting. • Secondary drying, during which the bond and residual moisture from the solid material are removed leaving a dry sample, a step that is important to preserve the stability of the sample. In shell pre-freezing, the sample in the lyophilized bottle is immersed in a low temperature heat transfer liquid, and the liquid sample is frozen along the inner wall of the lyophilized bottle to achieve a larger surface area. This thin layer of frozen layer allows water molecules to pass through more easily. Once the sample is frozen, it can be connected to the freeze-drying system. Primary and secondary drying occurs when the vial is attached to the lyophilization system and the sample is immediately exposed to a vacuum condition to overcome airflow resistance. At the same time heat is provided to make energy. The heat source that provides heat to the freeze-dried bottles and other glass containers in the drying oven or manifold is a room temperature air bath. In the case of automatic glanding, the heating layer is supplied. Conditions such as vacuum and heat help the water vapor sublimated from the ice to more easily flow away from the sample and the surface of the lyophilized material.
Several factors in the freeze drying process:
The sublimation efficiency of frozen samples depends on several factors. The difference in air pressure between the important frozen product and the collector. The effective freeze-drying of zui occurs when the sample is at a high temperature that it can withstand while still maintaining a frozen state, while the collector temperature and system vacuum are kept at a low value that can be achieved. The change in drying time depends on the eutectic temperature of the lyophilized material. For most biomaterials, this temperature is below 0oC, and some even down to -40oC. High air pressure differences and temperature differences will result in effective drying. After the primary freeze-drying is completed, all the ice is sublimed. However, the combined water is still present in the product. In the secondary drying, the dry phase of the zui is firmly bonded to the water of the solid sample, which is called the absorption of water into steam. This process is called desorption. Desorption is a slow process because the absorbed water is at a lower pressure than the liquid water at the same temperature. Freeze-drying is done completely when the vapor pressure of the sample and collector is equal. If the sample leaves the system prematurely when not completely dried, it may degrade quickly and lose structural and biological properties.