Freeze drying technology was used as early as World War II for the preservation and production of biological products such as plasma, antibiotics, and bacteria. When needed on the battlefield, dried products can be revived and used by adding physiological saline. After the war, it was mainly used for the production of biological products and drugs. In recent years, freeze-drying technology has been applied in various fields such as biological products, various foods, traditional Chinese medicine, chemical catalysts, ultra-fine materials, graphene, and concentrated powder production. Its characteristics of maintaining various properties, components, and tissue structures of raw materials unchanged, easy dissolution and preservation, have shown great potential for application and development in this field, and have attracted widespread attention from industry professionals.

Sublimation is a physical phenomenon (see figure). Under a certain vacuum environment, ordinary water only exists in two forms: ice and steam, and there is no liquid water. In this vacuum environment, water can only transform between the two forms of ice and steam with temperature changes. Using this principle, the dried material is pre frozen and then placed in a certain vacuum environment to gradually increase the temperature. The ice in the dried material will gradually sublime and become water vapor, leaving behind the dry material that has lost moisture. There is no liquid water present during the drying process.

The difference between ordinary drying and freeze-drying

Ordinary drying is the process of evaporating and separating water in liquid form from the dried material. For example, animals, plants, or slurries, these materials are mostly in a soft form. As the internal water migrates outward and evaporates, their solid form will fill the gaps left by the water molecules or come close to each other, causing collapse and agglomeration. The volume of the solid form left behind will shrink and become hard. During the process of water molecules migrating outward, some solutes carried by them will remain on the surface of the dried material, forming wrinkles and hard shells. Ordinary drying products generally encounter difficulties in reducing or dissolving in water.

Freeze drying is the process of sublimating and separating water from the dried substance in the form of solid ice. During the drying process, the dried substance has already frozen into a solid, and the gaps left by the sublimation of ice will not be filled by the solid substance. Naturally, there will be no collapse or aggregation, especially during the freezing process of the dried substance. The conversion of water to ice is accompanied by volume expansion, and the distance between the solid substance molecules will not only not decrease but also increase. Therefore, the dried substance left after freeze-drying is porous and fluffy, sponge like, very brittle, and easy to reduce or quickly dissolve in water when it comes into contact with water,

In drying practice, ordinary dried materials such as various animals and plants, as well as various powders, may encounter difficulties in rehydration and reduction, difficulty in dissolving in water, and even agglomeration after prolonged soaking, making it inconvenient to use. At the same time, the drying process is prone to contamination. The use of freeze-drying methods does not have these problems. The characteristic of freeze-dried products being able to recover or dissolve in water is something that ordinary drying methods cannot achieve. Its crispy texture also makes the taste of many vegetables, fruits, and even traditional Chinese medicine much better. Especially during the drying process, it is completely isolated from the outside world, safe and pollution-free. There is a clear difference between freeze-drying and ordinary drying.

Freeze drying characteristics

The freeze-drying process is carried out in a closed low-temperature environment completely isolated from sources of air, dust, bacteria, and other pollutants. The resulting dried products and raw materials have almost no changes, and the obvious advantages include

Keep the various components of the raw materials unchanged (including thermal sensitivity, functionality, biological activity, etc.);

02 Maintain the various properties of the raw materials unchanged (organizational structure, external characteristics, color, taste, etc.);

03 Porous and crispy, easy to crush and disperse;

04 is highly soluble in water and quickly rehydrates;

05 Dehydrates thoroughly, making it easy to store and transport for a long time.

Applicable scope of freeze-drying

·Biological products, drugs, and extracts

Biological agents, medicinal raw materials, nutrient solutions, reagents, plasma, snake and scorpion venom, bear bile, anthocyanins, ginkgo biloba extract, fungi, enzymes, antibiotics, etc;

·Chinese medicinal materials and health supplements

Ginseng, Gastrodia elata, Panax notoginseng, Cordyceps sinensis, Bird's nest, Dendrobium officinale, Frog oil, Goji berries, Polygonum multiflorum, Royal jelly, deer products, bovine colostrum, placenta, etc;

·Various types of food

Fruits: strawberries, raspberries, blueberries, mangoes, avocados, figs, lemons, apples, bananas, durians, various types of pulp, etc. Vegetables: scallions, garlic, yams, purple potatoes, etc. Instant soup ingredients;

Beverages: laver Egg&vegetable soup, seafood soup, coffee, fruit juice, etc;

Aquatic meat and poultry: sea cucumber, abalone, shellfish, shrimp, fish, beef and mutton, chicken, egg products, etc; Forest by-products: various edible fungi, wild vegetables, matsutake, bamboo fungus, asparagus, siraitia grosvenorii, konjac, etc.

·Non edible and industrial materials

Various flowers, ornamental plants and specimens, cultural relics, porous ceramics, catalysts, graphene, ultrafine materials, etc.