Preserved vegetable drying process
(1) Heating stage
The initial stage for preserved vegetable drying process is heating, and the appropriate temperature is 40°C-50°C.
(2) Constant speed drying stage
When the temperature of preserved vegetable rises to the wet bulb temperature of air energy, and all the heat absorbed from the air energy is used to evaporate water, the drying speed remains constant at this time. During the constant-speed drying stage, most of the preserved vegetable evaporates water as free water. The water evaporation rate of preserved vegetable is not entirely dependent on the temperature of the dry air, but also on the humidity of the air. The lower the relative humidity, the faster the moisture migration and evaporation.
(3) Deceleration drying stage
When the moisture evaporation rate of preserved vegetable reaches about 50-60%, the free water is greatly reduced, and part of the colloidal bound water begins to evaporate. At this time, the water diffusion rate of preserved vegetable slows down, which is lower than the water evaporation rate on the surface of the preserved vegetable.