Many materials need to undergo a series of pre-treatment processes before and after the beginning of drying. Next, I will introduce some common treatment methods.
- Product preheating: In the preheating stage, the initial temperature of the drying chamber is lower, and the moisture of the material evaporates less, so the humidity is relatively low. Only heating does not need to dehumidify, so the material can be quickly heated to the internal and external temperature balance. It usually takes 5 to 30 minutes.
- Inactivation treatment: The main function of inactivation is to destroy and inactivate the oxidase activity in fresh food through high temperatures, so that the material can not only maintain the original color and appearance, but also improve part of the aroma. Common materials that need to be completed are: tea, honeysuckle, day lily, chrysanthemum, Beijing chrysanthemum, pepper, star anise, green vegetables, etc.
- Dehumidification and color fixation: Dehumidification and color fixation is an effective method to protect the color of agricultural products. It is mainly achieved through rapid dehumidification at low temperatures. The temperature should not be too high. The temperature setting range is 45°C to 65°C.
- Product ripening: Ripening refers to the process of ripening, composition synthesis and material transformation by artificially providing suitable temperature and humidity. Among them, saccharification is also a kind of maturity. Common agricultural products that need to be ripened include sausages, tobacco leaves, persimmons, figs, sweet potatoes, etc.
- Material shrinkage rate: Only by reasonably controlling the dehydration rate of the material can the uniform shrinkage rate be achieved and the quality requirements of the material can be guaranteed. The requirements at this stage are very high, and a certain amount of experience is needed to be able to control scientifically and reasonably.
- Re-perspiration treatment: Artificial perspiration refers to stopping the heat pump drying equipment, so that the agricultural products can complete the moisture migration balance at a certain temperature. Natural perspiration is to push agricultural products out of the drying room and place them in the natural environment to complete the balance of water migration.
- Improve aroma: Deodorization is the final stage of drying. Through the action of high temperature, the production of aroma is promoted, the taste of agricultural products is becoming more and more intense, and the quality and value of product drying are improved. For spices and teas that require a high taste, they all need to go through this processing stage.
- Air-drying to regain moisture: The method of air-drying to regain moisture is very simple. After the entire drying process is completed, the material can be lowered to room temperature, so that the moisture of the agricultural product can reach a constant state, and then the packaging process can be carried out. If the content is too low, the final product will be directly packaged, which is easily broken, which can be avoided after the moisture is restored.