The Lyophilization equipment shall formulate different pre-freezing temperatures and pre-freezing holding time according to the characteristics of different substances. Different substances have their own sublimation temperature range, setting sublimation temperature and sublimation holding time. The Lyophilization Equipmentand holding time of the sample should be set according to the required water content of the freeze-dried substance. Work until freeze drying is over.
　　
According to the established temperature and holding time, a Lyophilization curve of freeze-drying temperature and time is established, and the freeze-drying curve is the relationship curve between the temperature and time of the freeze-drying oven laminate. With temperature as ordinate and time as abscissa. It directly reflects the change of laminate temperature at different times during the drying process.
　　
Generally, leafy vegetables are Lyophilization . Different experimental samples have different requirements for residual water. For long-term preservation of samples, the Lyophilization time will be long if the residual moisture content is very low. On the contrary, Lyophilization time can be short; The Lyophilization curve of a sample or a class of substances can only be found according to multiple tests so that high-quality Lyophilization samples and short Lyophilization time can be obtained.
　　
Lyophilization equipment is composed of refrigeration system, heating system and electrical instrument control system. Matters needing attention when using Lyophilization :
　　
1. the preparation of samples should expand its surface area as much as possible, which shall not contain acid and alkali substances and volatile organic solvents;
　　
2. the sample must be completely frozen into ice, if there is any residual liquid will cause gasification injection;
　　
3. pay attention to the cold trap is about 65 degrees below zero, can be used as a low temperature refrigerator, but must wear insulating gloves operation to prevent frostbite;
　　
4. Under normal circumstances, the machine shall not be used continuously for more than 48 hours.
　　
5. During the freezing process, the temperature of the sample gradually decreases. After the sample is taken out and warmed up for a period of time ( still in a frozen state ), it can be dried continuously to shorten the drying time.