Comparison with Liquid-Phase Drying


Lyophilization gives the opportunity to avoid denaturation caused by heating the product, by maintaining it frozen throughout drying. This is the most obvious advantage over liquid-phase drying.

Equally important is that in liquid-phase drying there is an undesirable shrinkage and concentration of active constituents that causes damage as well as a movement of these constituents to the surface of evaporation, where they form a dense, impermeable skin that inhibits drying, and later, rehydration. Such effects can be avoided by spray drying, but this requires brief exposure to temperatures around 100 C. Time-temperature profile

Further advantages of lyophilization for parenteral products are that the wet material can be accurately dispensed and can be sterile filtered just before filling into final containers so that particulate and bacterial contamination is reduced.

Thus, the principle advantages of lyophilization as a drying process are:

The principle disadvantages of lyophilization are:

Lyophilization should be used when the product meets one or more of the following criteria: unstable; heat liable; minimum particulates required; accurate dosing needed; quick; complete rehydration needed; high value.
Some other less common applications of lyophilization are recovery of water-damaged books and manuscripts and preservation of archaeological specimens, tissue for spare-parts surgery, museum specimens for display such as plants and animals, and vegetable matter for research programs.
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