Martin Christ Alpha 2-4 LDplus - Manual (Page 8)

8 General Information Operating Manual Freeze Dryer ALPHA 1-4 LDplus / ALPHA 2-4 LDplus
1. General Information
1.1. Introduction
What is freeze-drying (Lyophilisation)?
Freeze-drying means: Extraction of water from frozen material.
The drying process takes place by avoiding the liquid state through
sublimation, i. e. direct conversion from ice to vapour. This happens
under vacuum and the temperature in the product is normally less
than -10°C.
The aim of freeze-drying is to obtain an easily water soluble
product which will have the same characteristics as the original
product after addition of water.
As the drying process takes place in frozen state at very low
temperatures it is possible to dry e. g. proteins which will not
denature. Also most of the other chemical compounds will be
qualitatively and quantitatively unchanged.
Through freeze-drying the product, mainly of biological origin -
such as tissues, tissue extracts, bacteria, vaccines and sera - is
transformed into a dry product. During this process enzymatic,
bacterial and chemical changes are largely avoided.
Freeze-drying (lyophilisation) is the most gentle process for
preserving the biological properties of sensitive tissue and tissue
components.
Lyophilisation is also the best method when drying inorganic
products – e.g. nanoscale dispersions – the particle surfaces of
which should remain unchanged.