Put the pre-dried mushrooms on the drying tray. After leveling, put the tray into the material truck layer by layer. The overall height of the material truck is controlled at about 1.7 meters, and it should be divided into about 10-13 layers. In this way, the hot air flow is smooth during the drying process, the heating is uniform, and the drying and dehumidification effect is good.
1 Preparatory period
Dry the harvested mushroom in a heat pump dryer with a temperature of 35°C for 1-4 hours to reduce the water content by 15-20%. The drying temperature should not be too high or too low, and it should be controlled at 35 °C. At this time, the air inlet and exhaust holes should be fully opened, the temperature return hole should be closed, and drying should be carried out for 3-4 hours. Generally, the temperature increases by 1°C-2°C per hour, and the temperature should gradually rise to about 40°C.
2 Mushroom constant speed drying period
During this drying period, the water diffusion rate inside the fresh mushroom body and the surface evaporation rate are basically equal. Generally speaking, after drying for 4-5 hours, the temperature should gradually rise to about 50 °C, and should rise about 2 °C per hour. The air intake and exhaust holes should be closed by 1/3. This stage is generally dried for 3-4 hours. . At this stage, the temperature should be controlled between 40°C and 50°C. During this period, the fresh mushrooms are softened. As time goes on, the evaporation of the water and hardening of the body starts from the edge of the mushroom umbrella and moves to the thick part of the center. At this stage, the mushroom cap is going into shape. As the mushroom core still has moisture and the temperature is only up to 50 °C, the gills will not show light yellow.
3 post-drying stage
At this stage, the water in the mushroom body begins to decrease, the free water is basically drained, and part of the bound water is gradually drained out during the drying process. During this period, the water movement speed in the fresh mushroom body obviously cannot keep up with the surface evaporation speed, and the ventilation volume can be appropriately reduced to save energy. In this period, the drying temperature should be maintained at 50℃-55℃, which is consistent with the temperature inside and outside the mushroom. The air inlet and exhaust holes should be closed by 1/2, the temperature return hole should be opened by 1/2, and the drying time should be 2-3 hours. At this stage, the mushroom turns pale yellow and begin to produce fragrance.