The practical application of freeze-drying can be traced back to the Inca people of Peru in South America, who used it to store potatoes and other crops. The cold temperatures on the mountain of Machu Picchu would freeze the crops, while the low air pressure at high altitudes would cause the moisture in the food to evaporate gradually. This practice by the Inca people resembles a primitive form of freeze-drying technology. Currently, this technique is often used for preserving pharmaceuticals, valuable herbs, and ingredients. Even NASA utilizes freeze-drying technology to produce food for astronauts in space.

In fact, freeze-drying combines the techniques of “freezing,” “vacuum,” and “drying.” The principle involves freezing the substance first and then creating a vacuum. At this point, the moisture present in the substance will directly sublimate from solid ice to a gaseous state and be expelled. This physical process effectively removes a large amount of moisture from the food, reducing the moisture content to below 5%. This prevents the conditions for microbial growth and meets the hygiene and safety standards for shelf-stable food without the need for preservatives. Therefore, freeze-drying is a technology that makes it easier for food to be stored at room temperature for an extended period. Refrigeration or freezing, on the other hand, can lead to moisture absorption and a shortened shelf life.