Freeze-drying refers to the process of removing moisture or other solvents from frozen biological products by sublimation. Sublimation refers to the process in which a solvent, such as water, changes from a solid state to a gaseous state without going through a liquid state like dry ice. The product obtained by freeze-drying is called lyophilizer, and the process is called lyophilization. Why choose freeze-drying? Traditional drying will cause the material to shrink and damage the cells. The structure of the sample will not be destroyed during the freeze-drying process, because the solid component is supported by the solid ice in its place. As the ice sublimates, it will leave pores in the dry remaining material. This preserves the integrity of the product's biological and chemical structure and its activity.
In the laboratory, freeze-drying has many different uses, and it is indispensable in many biochemical and pharmaceutical applications. It is used to obtain biological materials that can be stored for a long period of time, such as microbial culture, enzymes, blood, and drugs. In addition to the stability of long-term storage, it also retains its inherent biological activity and structure. For this purpose, lyophilization is used to prepare tissue samples for structural studies, such as electron microscopy studies. Freeze-drying is also used in chemical analysis. It can obtain dry samples or concentrate samples to increase the sensitivity of the analysis. Freeze-drying stabilizes the sample composition without changing the chemical composition, and is an ideal analytical aid. Realization of freeze drying: Freeze drying can occur naturally. Under natural circumstances, this process is slow and unpredictable. Through the freeze-drying system, people improved and subdivided many steps to speed up the process. Freeze-drying system: A basic freeze-drying system includes: · a drying chamber or manifold · an evacuation system to overcome obstacles and accelerate gas flow · a heat source to provide energy · a low-temperature condenser to maximize vapor pressure Freeze and trap the steam to prevent it from contaminating with water vapor. The freeze-drying process of the vacuum pump contains three steps: · Pre-freeze, prepare samples for the next sublimation process. · Primary drying, during which the ice sublimates without melting. · Secondary drying. During this process, the residual moisture bound to the solid matter is removed, leaving a dry sample. This step is very important for the stability of the preserved sample. In shell pre-freezing, the sample in the lyophilized bottle is immersed in a low-temperature heat-conducting liquid and rotated, and the liquid sample freezes along the inner wall of the circumference of the lyophilized bottle to achieve a larger surface area. This thin layer of freezing allows water molecules to pass through more easily. Once the sample freezes, it can be connected to the freeze-drying system. Primary and secondary drying occurs when the sample vial is connected to the lyophilization system, and the sample is immediately exposed to a vacuum condition, thereby overcoming the resistance of the airflow. At the same time heat is provided to make energy. The heat source for providing heat to lyophilized bottles and other glass containers connected to the drying cabinet or manifold is a room temperature air bath. On the automatic gland cover box, it is supplied by heating layer. Vacuum and heat conditions can help the water vapor sublimated from the ice to flow away from the sample and the lyophilized material on the surface more easily. Several factors of the freeze-drying process: The sublimation efficiency of frozen samples depends on several factors. The most important air pressure difference between the frozen product and the collector. The most effective freeze-drying occurs at the highest temperature that the sample can withstand while still maintaining the frozen state, while the collector temperature and system vacuum are kept at the lowest possible values. The drying time varies depending on the eutectic temperature of the freeze-dried material. For most biological materials, this temperature is lower than 0oC, and some even lower to -40 oC. High air pressure difference and temperature difference will produce effective drying. After the primary freeze-drying is completed, all the ice is sublimated. However, bound water still exists in the product. During secondary drying, the final phase is dried, and the water that is firmly bonded to the solid sample is called absorbed water and turns into steam. This process is called desorption. Desorption is a slow process because absorption water has a lower gas pressure than liquid water at the same temperature. Freeze drying is completed when the vapor pressures of the sample and the collector are equal. If the sample leaves the system prematurely before it is completely dried, it may degrade quickly and lose structure and biological properties.
In the laboratory, freeze-drying has many different uses, and it is indispensable in many biochemical and pharmaceutical applications. It is used to obtain biological materials that can be stored for a long period of time, such as microbial culture, enzymes, blood, and drugs. In addition to the stability of long-term storage, it also retains its inherent biological activity and structure. For this purpose, lyophilization is used to prepare tissue samples for structural studies, such as electron microscopy studies. Freeze-drying is also used in chemical analysis. It can obtain dry samples or concentrate samples to increase the sensitivity of the analysis. Freeze-drying stabilizes the sample composition without changing the chemical composition, and is an ideal analytical aid. Realization of freeze drying: Freeze drying can occur naturally. Under natural circumstances, this process is slow and unpredictable. Through the freeze-drying system, people improved and subdivided many steps to speed up the process. Freeze-drying system: A basic freeze-drying system includes: · a drying chamber or manifold · an evacuation system to overcome obstacles and accelerate gas flow · a heat source to provide energy · a low-temperature condenser to maximize vapor pressure Freeze and trap the steam to prevent it from contaminating with water vapor. The freeze-drying process of the vacuum pump contains three steps: · Pre-freeze, prepare samples for the next sublimation process. · Primary drying, during which the ice sublimates without melting. · Secondary drying. During this process, the residual moisture bound to the solid matter is removed, leaving a dry sample. This step is very important for the stability of the preserved sample. In shell pre-freezing, the sample in the lyophilized bottle is immersed in a low-temperature heat-conducting liquid and rotated, and the liquid sample freezes along the inner wall of the circumference of the lyophilized bottle to achieve a larger surface area. This thin layer of freezing allows water molecules to pass through more easily. Once the sample freezes, it can be connected to the freeze-drying system. Primary and secondary drying occurs when the sample vial is connected to the lyophilization system, and the sample is immediately exposed to a vacuum condition, thereby overcoming the resistance of the airflow. At the same time heat is provided to make energy. The heat source for providing heat to lyophilized bottles and other glass containers connected to the drying cabinet or manifold is a room temperature air bath. On the automatic gland cover box, it is supplied by heating layer. Vacuum and heat conditions can help the water vapor sublimated from the ice to flow away from the sample and the lyophilized material on the surface more easily. Several factors of the freeze-drying process: The sublimation efficiency of frozen samples depends on several factors. The most important air pressure difference between the frozen product and the collector. The most effective freeze-drying occurs at the highest temperature that the sample can withstand while still maintaining the frozen state, while the collector temperature and system vacuum are kept at the lowest possible values. The drying time varies depending on the eutectic temperature of the freeze-dried material. For most biological materials, this temperature is lower than 0oC, and some even lower to -40 oC. High air pressure difference and temperature difference will produce effective drying. After the primary freeze-drying is completed, all the ice is sublimated. However, bound water still exists in the product. During secondary drying, the final phase is dried, and the water that is firmly bonded to the solid sample is called absorbed water and turns into steam. This process is called desorption. Desorption is a slow process because absorption water has a lower gas pressure than liquid water at the same temperature. Freeze drying is completed when the vapor pressures of the sample and the collector are equal. If the sample leaves the system prematurely before it is completely dried, it may degrade quickly and lose structure and biological properties.
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