Lyophilization is a drying or dehydration process that is carried out by progressive sublimation of the solvent or water present in a sample. This process is characterized by using low temperatures which favors that some volatile elements are not lost, otherwise it occurs in conventional drying processes. In progressive sublimation, the direct passage from ice (solid) to gas (vapor) is achieved without going through its liquid phase. This process is carried out in equipment called a lyophilizer that allows to obtain a product that can easily be rehydrated and that can fully recover its properties once said rehydration is carried out.
A lyophilizer is an extremely necessary piece of equipment when you want to preserve products, since it allows you to eliminate moisture through cold drying. The material to be lyophilized is introduced into the equipment, where very low temperatures are handled, normally less than – 40 ° C. With a vacuum pump, the pressure in the equipment is reduced. Having reduced the temperature the water or organic solvent freezes. Later, when the pressure is lowered, the water that is in the solid state turns into steam in the process known as sublimation.
Operation of a freeze dryer
You should know that to introduce any material into the lyophilizer, it first needs to be frozen, in order to maintain its molecular structure. To achieve this, a freezer capable of reaching sub-zero temperatures is used. The frozen material is introduced into the lyophilizer, where there is a vacuum pressure, thanks to the action of a vacuum pump, which allows it to function correctly. Due to the vacuum, 95% of the water present in the sample is sublimated. In this way, the product dries without the need to use temperatures above room temperature.
The heat contained in the lyophilizer provides the necessary energy to the water to turn into a gaseous state, accelerating the process. And the gas that remains loose is condensed at low temperatures, returning to a solid state again.
Benefits offered by freeze drying
- Products are obtained that can be regenerated very quickly.
- The shape and characteristics of the final product are essentially the original ones.
- It is an ideal process for drying thermolabile substances.
- Oxidizable constituents are protected.
- The final moisture content is very low.
Freeze-dried products can be stored for long periods of time with the retention of the physical, chemical, biological and organoleptic properties of their original states. Lyophilization reduces quality losses caused by chemical reactions, enzymatic and non-enzymatic degradation. Oxidation processes can be controlled by storing lyophilized products in oxygen-impermeable containers. Storing lyophilized products in places with low temperatures avoids protein denaturation.
Stages of lyophilization
- Dry Chamber: Here the element to be lyophilized is positioned inside the dry chamber, which is generally transparent, and allows the entire process to be visually monitored. In this stage, all the water vapor contained in the sample is released.
- Condenser: Subsequently, the condenser with a cooling circuit generates the sublimation of the released water vapor. For this, there will be a drop in temperature between -50 ° C and -125 °
- Vacuum system: By means of a vacuum pump, the vapors produced are eliminated to prevent them from damaging the sample. This pump is also essential in the first two stages of the process, maintaining an optimal environment for proper lyophilization.
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