The difference between freeze drying and ordinary drying

Freeze drying and ordinary drying have significant differences in principles, processes and applications.

The difference in principle
Freeze drying: It is a drying method performed at low temperature, usually below 0℃, for the purpose of storing items. It removes moisture by first freezing the material to be dried into a solid, and then vaporizing the moisture in it through sublimation under vacuum conditions. This process will not affect the agglomeration state of solid particles, so the original particles can be preserved intact and not be compressed and agglomerated.

Ordinary drying: including sun drying, boiling drying, oven drying, spray drying and vacuum drying, etc. These methods are usually performed at temperatures above 0°C or higher. They evaporate water by heating, but due to the higher temperature, some volatile components in the substance may be lost, and some heat-sensitive substances may be denatured or deactivated.

Differences in process
Freeze-drying: During the freeze-drying process, the moisture in the substance is first frozen into ice crystals, and then under vacuum conditions, the ice crystals directly sublimate into water vapor, thereby achieving the purpose of drying. This process can be carried out at lower temperatures, usually no more than 40°C.

Ordinary drying: In ordinary drying, the water in a substance is evaporated by heating, and the water vapor is then carried away by air flow or other means. This process typically requires higher temperatures and may result in changes in the color, shape, and texture of the substance.

Differences in application
Freeze-drying: widely used in the fields of chemistry, pharmaceutical industry, food industry and scientific research, especially in biopharmaceuticals containing biologically active substances. It is suitable for processing substances that easily deteriorate or lose activity at high temperatures.
General drying: suitable for various types of substances, including food, pharmaceuticals, chemical products, etc. It is a versatile drying method but may be limited when working with some heat-sensitive materials.

Advantage comparison
Freeze drying:
Many heat-sensitive substances do not undergo denaturation or inactivation.
When drying at low temperatures, some volatile components in the substance 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 occurs.
Since the moisture in the material exists in the form of ice crystals after pre-freezing, the dissolved inorganic salts originally dissolved in the water are evenly distributed in the material. During sublimation, the dissolved substances dissolved in the water are precipitated, which avoids the phenomenon of surface hardening caused by the precipitation of inorganic salts carried by the internal moisture of the material migrating to the surface in the general drying method.

Normal drying:
The equipment is simple and easy to operate.
It has a wide range of applications and can handle various types of substances.
The drying speed is fast and the efficiency is high.
Freeze drying and ordinary drying each have their own characteristics and scope of application. The choice of drying method depends on the specific substance and drying purpose.