Compared with the conventional method, the freeze-drying method has the following advantages:

* Many heat-sensitive substances do not denature or inactivate.

* When drying at low temperature, some volatile components in the material are lost very little.

* During the freeze-drying process, the growth of microorganisms and the action of enzymes cannot proceed, so the original properties can be maintained.

* Since it is dried in a frozen state, the volume is almost unchanged, the original structure is maintained, and no concentration phenomenon occurs.

* Since the water in the material exists in the form of ice crystals after pre-freezing, the dissolved inorganic salts originally dissolved in water are evenly distributed in the material. During sublimation, the dissolved substances dissolved in water are precipitated, which avoids the phenomenon of surface hardening caused by the precipitation of inorganic salts carried by the migration of moisture from the material to the surface in the general drying method.

* After drying, the material is loose and porous, and it is sponge-like. After adding water, it dissolves rapidly and completely, and restores its original shape almost immediately.

* Since drying is carried out under vacuum with very little oxygen, some oxidizable substances are protected.

* Drying can remove more than 95% to 99% of the moisture, so that the dried product can be stored for a long time without deterioration.

* Because the material is in a frozen state and the temperature is very low, the temperature of the heat source for heating is not high, and a heater with normal temperature or low temperature can meet the requirements. If the freezer compartment and the drying room are separated, the drying room does not need to be insulated, and there will not be a lot of heat loss, so the utilization of heat energy is very economical