What is a freeze dryer, and how does it work?

Freeze Dryer over time, humans have always sought ways to preserve various materials. From primitive methods like salting and smoking to today’s advanced techniques, this effort has continued. Among these developments, the freeze dryer is considered a turning point in the material preservation and processing industry.

This technology, rooted in scientific research from the mid-20th century, has become one of the most efficient methods for drying sensitive materials. By utilizing complex physical principles, the freeze dryer preserves the structure and properties of materials during the drying process, which is crucial for many industries, including pharmaceuticals, food, and biotechnology.

 

A freeze dryer is an advanced device that utilizes the lyophilization process to dry materials. This process comprises three main steps, each playing a crucial role in maintaining the quality of the dried material.

In the first step, the material is rapidly frozen to a temperature between- 40 and- 50 degrees Celsius. The speed of this freezing is critical as it prevents the formation of large ice crystals that can damage the cellular structure of the material. This rapid freezing results in tiny ice crystals that help preserve the original structure and texture of the material.

In the second step, called primary drying, the pressure in the device’s chamber is sharply reduced to create vacuum conditions. Then, by applying controlled heat, the ice in the material directly converts into vapor through sublimation, a process that occurs without passing through the liquid state. This step is typically the longest part of the process, taking from several hours to several days, depending on the type and volume of the material. During this phase, approximately 95% of the moisture in the material is removed.

Finally, a secondary drying step is performed, during which the remaining moisture that is molecularly bound to the material is eliminated by increasing the temperature while maintaining the vacuum conditions. This final step is often time-consuming and can last several hours. The temperature of the product in this stage may exceed zero degrees Celsius, yet it remains in vacuum conditions. The goal of this step is to reduce the final moisture content of the product to below 1%.

Freeze dryers find use in various industries, including food, pharmaceutical, and biotechnology. In the food industry, this method is employed to produce products such as instant coffee, dried fruits, and high- quality dried vegetables. In the pharmaceutical sector, it is used to produce vaccines, antibiotics, and other heat- sensitive drugs. It is also applied in scientific research to preserve biological samples.