Freeze Drying

Freeze Drying (Lyophilization)


Lyophilization or freeze drying is a significant procedure in the preparation of a sample and for the storage and preservation of foods, biological, and pharmaceuticals. There are numerous techniques involving dehydration, but freeze drying is particularly suitable for heat sensitive substances.

Lyophilization has been utilized extensively in food processing, for example, in whole dinners and coffee processing. Besides, the process has been employed widely in pharmaceuticals development, for example, the creation of antibiotics, including the preservation and storage of biological like cell lines, proteins, viruses, and plasma.

How do you accomplish Freeze Drying?

The procedure whereby solvents or water is extracted from a material that is frozen by altering the water that is frozen directly into vapor with no in-between formation of liquid water is what is referred to as Lyophilization or freeze drying.

The ground for this process of sublimation involves heat absorption by the sample that is frozen so that the ice can be modified to vapor, employing vacuum pump to increase water vapor extraction from the sample surface and then the water vapor is put on a collector. Lastly, the collector removes the heat so that the water vapor can be condensed.

This simply means that the freeze drying procedure is a balance between the heat detached from the collector to modify the water vapor to frozen water and the heat engrossed by the sample to vaporize the frozen water.

Benefits of Freeze Drying

  • Liquid processing is done with ease, and it makes aseptic handling simple
  • Increased stability of the product in a dry state
  • Water can be removed from the product without excess heating
  • Easy and fast recomposed product termination

The process of Freeze Drying

Lyophilization is majorly employed in extracting water from products that are sensitive, specifically those with biological roots. This process should be done without destroying the products so that their preservation can be easy, in a storable state that is enduring, and be recomposed by simply adding water.

Good examples of products that have been freeze dried include; bacteria, vaccines, serum, antibiotics, cells, tissues, and biotechnical products just to mention but a few. Atmospheric pressure is used to free the dried product, then in the first drying stage known as the primary drying, the frozen water is removed through the process of sublimation. Second is a stage called secondary drying where the water is removed by a process of desorption.

The process is done under a vacuum. The procedure has suitable conditions that will determine the freeze dried product’s quality.

Below are some of the facets to be considered while engaging in the procedures regarding freeze drying:

  1. Freezing– Transforming or modifying a basic product by removing heat to develop a situation that is suitable for drying through sublimation. At first, the formation of crystal nuclei is developed when an aqueous product is cooled. After that, crystals of dissimilar shapes and sizes will be formed when the water in the surroundings is taken around this nucleation sites.

Decisive factors in determining the crystal size and shape, including the influence on the process of sublimation are water content, liquid viscosity, basic product composition, non-crystallization substance presence, and the speed of freezing.

  1. Primary Drying– The initial stage of the primary drying involves ice sublimation process on the surface. As the procedure carries on, the surface that is subliming withdraws into the product, and the vapor that is evolving ought to be conducted via the previously dried outer layers. The process of drying simply depends on the vapor speed elimination and transmission as well as the required sublimation heat.

The sublimation heat is offered to the product by thermal and convection conduction, including a small section of the thermal radiation. The heat transmission by convection should be optimized apart from the thermal radiation and conduction. Nonetheless, it is important to note that convection will stop in the drying chamber due to the pressure reduction at below ten millibars.

This is the reason pressure has to be adjusted to the highest permissible value in primary drying. The heat for sublimation is only required at the ice core boundary which is retreating into the product’s center during the process of drying.

Care ought to be taken to uphold the needed temperature of sublimation during drying. The highest acceptable temperature for a product that is drying ought not to be surpassed. The primary drying stage carries on until all the frozen water in the product has sublimed.

  1. Secondary drying– The last drying stage has the objective of reducing the moisture content that is residual from the product. This is important to make sure that the product is in a storable state that is permanent. The moisture bound by adsorption in the product’s internal surface ought to be extracted.

Overcoming the capillary water forces is frequently necessary to achieve this and freeze drying plant ought to be structured to give a high-pressure gradient in the secondary drying stage. In most cases, it is impossible to increase the product’s temperature without destroying the product. This process ought to be controlled to avoid any procedure that will result to over drying.

  1. After treatment– This factor evaluates how products that have been dried can be protected or guarded. Logically speaking, it is necessary that vials, bottles or flasks with dried products be closed immediately before being transferred from the plant.

There are unique ribbed stoppers positioned on the vials or bottles’ neck, and the containers may be sealed under guarded gas environment or vacuum. The product determines method selected.

  1. Equipment– Absolute Pharmacy uses twenty-four sq ft cGMP freeze dryers to assure our clients and customers of a dependable authenticated cycle that have the ability to produce an extensive range of pharmaceutical goods.


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