Lyophilization and freeze drying have the same meaning. Lyophilization is a method of extracting water that is commonly employed to protect perishable substances, prolong their shelf life, or make them easier to transport. The process involves freezing the material and then reducing pressure and applying heat to allow the frozen water within the material to transform directly into vapour.
The Three Key Phases of Lyophilization
Lyophilization, which happens in three stages, begins with the freezing phase, which is regarded as the most crucial. Effective lyophilization techniques have the potential to decrease drying durations by approximately 30%.
Phase 1 – Freezing Phase
In the realm of freezing products, there exist multiple techniques. Preservation can be achieved through freezing in a standard freezer, immersing in a chilled bath known as a shell freezer, or placing on a shelf within a freeze dryer. By Cooling the material below its triple point, sublimation is favoured over melting, effectively maintaining its original physical state and structure.
Lyophilization can be achieved most effectively by generating sizable ice crystals, which can be achieved through gradual freezing or annealing. However, in the case of biological substances, excessively large crystals can cause damage to cell walls, resulting in suboptimal outcomes during the freeze-drying process. To mitigate this issue, the freezing process is conducted rapidly. For materials prone to precipitation, annealing can be employed, which entails rapid freezing followed by increasing the temperature of the product to facilitate crystal growth.
Phase 2 – The Crucial Sublimation Stage of Primary Drying
During the second phase of lyophilization, known as primary drying or sublimation, the pressure is reduced, and heat is applied to facilitate the sublimation of water from the material. The sublimation process is expedited by creating a vacuum, while the presence of a cold condenser ensures that the water vapour adheres and solidifies. Additionally, the condenser serves to protect the vacuum pump from the water vapour. This phase is responsible for eliminating approximately 95% of the water content in the material. However, it is important to note that primary drying must be conducted carefully as excessive heat can potentially alter the material’s structure.
Phase 3 – The Second Phase of Drying: Adsorption
During the secondary drying phase of lyophilization, which is also known as
adsorption, the process removes the water molecules that are bound ionically. This is achieved by increasing the temperature beyond what was used in the primary drying phase, which causes the bonds between the material and the water molecules to break. As a result, the materials that undergo freeze-drying maintain their porous structure. Once the lyophilization process is finished, an inert gas can be used to break the vacuum before sealing the material. It is generally possible to dry most materials to a residual moisture level of 1-5%.
Freeze-Drying in the Pharma Sector
Lyophilization, also known as freeze-drying, is a widely utilised technique in both the food and pharmaceutical industries. Its primary purpose is to preserve various substances, such as food products and pharmaceuticals, specifically biopharmaceuticals, which often possess intricate molecular structures that are prone to instability in liquid form. Storing these medications without removing moisture significantly limits their shelf life. However, by subjecting them to the lyophilization process, the moisture is effectively eliminated, thereby considerably enhancing their stability and allowing for extended storage. When needed, these lyophilized pharmaceutical materials can be reconstituted by reintroducing moisture. Examples of medications commonly subjected to lyophilization include antibiotics, vaccines, bacteria, and diagnostic drugs.
Challenges with Lyophilization
Lyophilization poses numerous challenges that necessitate a comprehensive understanding of its intricacies. One such challenge is the varying composition of substances or drugs, which requires a meticulous examination of the lyophilization process for each material. It is imperative to ensure that All aspects and components of the process are perfectly tailored to the specific material in order to minimise the risk of damage. Conducting such research demands a significant investment of both time and expertise. Moreover, the prolonged exposure of products to the environment during the lyophilization process introduces a contamination risk. Thus, ensuring sterility in lyophilization, particularly for drug-related applications, necessitates strict adherence to safety regulations. However, the extensive use of a
lyophilization service on a large scale can result in substantial costs.
