Beyond Freeze-Drying - Freeze-drying of Pharmaceuticals and Biopharmaceuticals - page 177

Figure 4 Comparative gel electrophoresis patterns of fresh (in aqueous glycerol solution)
PST 1 Restriction Enzyme produced digest with a ''Ready-To-Go'' dried
preparation, after 5-month storage at ambient temperature (see Franks et al.) 160
13.4 Comparisons with Freeze-Drying
Advantages of evaporative drying over freeze-drying include:
(i) Capital equipment less expensive; freeze-drying equipment can be
used.
(ii) Shorter processing time; lower energy requirements.
(iii) More reliable process monitoring and control (water removal
does not rely on stochastic - uncontrollable - processes like ice
nucleation).
(iv) Enhanced long-term stability at ambient, even elevated temper-
atures.
(v) Water is removed from the system permanently in a single step.
(vi) Spray drying lends itself to continuous processing.
Disadvantages of evaporative drying include:
(i) Necessity of powder filling may create sterility problems.
(ii) Spray drying requires large volumes of purified gas.