Freeze Dried Food

Freeze Dried food has the advantage of maintaining its freshness and nutritional content and can be kept at room temperature for more than five years without preservatives. It first appeared on the menu of Apollo moon astronauts. Because of its lightweight, easy to carry and transport, freeze-dried food began to enter People's Daily life, has become a leisure and convenient health food.

At present, the types of freeze-dried food in China are still relatively conventional, including freeze-dried fruit slices, freeze-dried vegetables, freeze-dried beef, and soup. The most common is the "vegetable beef" seasoning package in the instant noodles, the dehydration rate can reach 95%.

Achieving such high rates of dehydration and locking in the nutrients of the food itself depends on the dark technology of the food industry, lyophilization. The technology, which originated in Russia in the 1940s, is relatively new to China, where it has a mature supply chain, mostly for export.

How the technology works are not complicated. Simply put, lyophilization is a sublimation of frozen products. Sublimation occurs when a frozen liquid begins to turn into a gaseous state. The whole freeze-drying process mainly includes three stages: pre-freezing, primary drying, and secondary drying.

Freeze-dried food must first be to precool below the eutectic temperature, also is the first material of frozen food (solute), and then through the sublimation from food to remove the ice, requires careful control of temperature and pressure at this moment two parameters, sublimation rate depend on the vapor pressure of food and the difference between the vapor pressure of ice, molecules from high-pressure sample moves to samples of low pressure, due to the vapor pressure and temperature, so the food must also be higher than the set temperature ice temperature. After the first drying, all the ice in the food sublimates, there is still some liquid in the food, through the second drying to completely remove the excess water. This process is also called isothermal desorption, where excess water is desorbed at high temperatures.

In the whole process of lyophilization, accurate freezing methods and proper storage are very important. With the continuous exploration and development, today's freeze-drying technology is also very mature, in foreign countries, freeze-dried food is very popular, even often in short supply.