Frequently Asked Questions
What is Lyophilization?
Lyophilization is another word for "freeze-drying". The typical process includes water-removal (for perishables) and the natural shrinkage of the subject material. Freeze-dried materials are also more suitable for shipment than the original materials. To achieve the desired result, the subject materials are frozen (to very cold temperatures); then heated in order to remove moisture. The result is a lyophilized (freeze dried) material.
What are the 3 phases of lyophilization?
1. Freezing:
Different materials require different methods of freezing. For some materials, using a purpose-built freezer will produce a satisfactory result. Other methods include either a freeze-drying apparatus or a chilled bath. Determining a material's "triple point" is key. In order to freeze-dry, its temperature must drop below this point--if the materials are too "warm" they may not simply yield their water, they may actually melt. Proper freezing will preserve the material's proper form. For some materials, slow-freezing (also called "annealing") is suitable; but with biological materials this method can produce ice-crystals too large to maintain the materials' integrity. For these materials, freezing is rapid, rather than gradual. 2. Sublimation: Here the pressure is lowered and the material is heated in a vacuum. This allows the water to sublimate, or "drain out" of the material. About 95% of moisture is removed in this phase, but it can take some time. Temperature must be carefully monitored to keep from altering the molecular structure of the material. 3. Adsorption (Secondary Drying): This is the final phase of the process. Here, the last few water molecules are removed by raising the temperature higher than the primary drying temperature. This tends to break down the chemical adherence of the water molecule to the subject materials, leaving a somewhat porous result. Most materials end up with between 1 and 5% of the original moisture content. What are the lyophilization challenges?
Everything depends on carefully regulating temperature. For instance, if the material is overheated, it can either melt or collapse. If temperature isn't properly regulated, excess vapor can develop and the freezer's condenser will not perform optimally, which will result in a degraded product. If too much vapor is produced too quickly, it can create unwanted pressure in the freezing chamber--also leading to a degraded result.
Terminology:
Eutectic Temperature: this is the minimum melting temperature, but it's not universal. Some materials have no eutectic point--or several.
Critical Temperature: this is the maximum temperature the material will support before it melts or collapses Crystalline: A material that forms crystals when frozen is called "crystalline". Amorphous: Mixed materials that don't crystallize, but can turn into a glassy substance. For these materials, the temperature needs to get below the "glass formation" point. Collapse: As the name suggests, collapsed materials have lost their internal structure, and are prone to incomplete drying, relative inability to dissolve properly, and "ablation" (erosion of surface and loss of integrity) Do you have any questions? Get in touch today!
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Hudson Valley Lyomac Freeze Dryers are designed and manufactured in the USA.
Freeze Dryer Models*: • STRATUS MP3® Series • TRILOGY® Series • TRIDENT® Series • FUTURA® Series • BT-1000 Bench-Top Lyophilizer Trilogy®, Trident® and Futura® are registered trademarks of lyophilizers manufactured by Hudson Valley Lyo Mac, Inc. *Each model can be customized for size and application |