The optimal drying temperature for Rehmannia is generally between 50°C and 60°C. Temperatures above 70°C will destroy its active ingredients. If the temperature is too low, the drying time will be prolonged, affecting drying efficiency and quality. Therefore, selecting the appropriate drying temperature is crucial for the quality and yield of Rehmannia.

Humidity is also a key parameter that needs to be controlled when drying Rehmannia. Excessive humidity can degrade the quality of the Rehmannia and increase the presence of microorganisms such as mold and bacteria, affecting the safety and shelf life of the medicinal material. Therefore, it is crucial to control the drying process by selecting the appropriate drying time, temperature, and humidity.

The drying time for Rehmannia is generally around 4-7 hours, with the specific time depending on factors such as the moisture content, temperature, and humidity of the medicinal material. Generally speaking, the longer the drying time, the darker the Rehmannia leaves and the lower the quality of the medicinal material. Therefore, the drying time must be carefully controlled to ensure the quality and yield of Rehmannia.

Common Questions and Precautions:

1. Regularly check the temperature, humidity, and drying time during drying to ensure the quality and effectiveness of the Rehmannia. 2. Avoid mixing Rehmannia root with other debris during drying to avoid compromising the purity of the medicinal product.
3. When drying in bulk, ensure proper height and good ventilation to avoid overlapping leaves.
4. Never use a high-temperature oven or sun-dried hay to dry Rehmannia root, as this may result in excessive loss of the active ingredients and affect its efficacy.