Drying and shaping are the core processes that determine the quality of finished products in scenarios such as leaf specimen production, flower and leaf cultural and creative activities, and leaf raw material processing. Traditional processes such as natural air drying, hot air drying, and compressed air drying commonly suffer from problems such as slow drying, easy deformation, variable color, and uneven dryness and wetness, making it difficult to meet standardized, high-quality, and high-efficiency processing requirements. Microwave drying technology is perfectly adapted to the material characteristics of light and thin leaves, high moisture content, fragile texture, and easy oxidation deformation, becoming the preferred process for rapid drying and shaping of leaves.
Traditional drying belongs to surface heat transfer heating, relying on hot air and heat sources to gradually conduct heat from the surface of the leaves inward, and the moisture evaporates layer by layer from the outside to the inside. This heating method has natural shortcomings: the rapid loss of moisture on the surface of the leaves will form a dense dry film after drying, which hinders the continuous evaporation of internal moisture and ultimately leads to problems of external dryness and internal wetness, uneven dryness and wetness. Not only is it not completely dried, but it is also prone to moisture and mold growth after storage.
Microwave drying adopts the principle of dielectric heating, which is completely different from the traditional heat transfer mode. Microwaves can penetrate the entire material of leaves and directly act on the polar water molecules inside the leaves, causing them to rub and vibrate at high speed in a high-frequency electromagnetic field, instantly generating heat, achieving synchronous heating of the whole and simultaneous dehydration inside and outside. The entire process does not require thermal conduction transition, avoiding the problem of surface dryness and water locking from the root, allowing the moisture in the leaves to evaporate evenly and thoroughly.
The moisture content of fresh leaves is extremely high, generally reaching over 75%, and the leaves are light, thin, and delicate. Traditional drying processes take a long time. Natural drying takes several days, and hot air drying also takes several hours to complete dehydration. The long processing process will cause continuous oxidation reactions and microbial growth in the leaves, making them prone to yellowing, blackening, and decay.
The penetrating heating characteristics of microwave technology can compress the drying and shaping cycle of tree leaves from hours to minutes. Under the controllable operating conditions of microwave equipment, leaves can quickly complete overall dehydration and shaping, with water evaporation rate much faster than oxidation and deterioration rate, greatly reducing the time for materials to be exposed to the air. It can not only quickly complete the drying process, but also effectively avoid phase loss caused by long-term processing, adapting to the production needs of batch and rapid leaf processing.
In addition, microwave drying can achieve low-temperature rapid dehydration, and the conventional processing temperature is controlled in the low-temperature range of 60-80 ℃ to avoid the damage of high temperature to the nutritional components and color structure of leaves. Meanwhile, microwave has unique biological effects, which can kill microorganisms and insect eggs on the surface and inside of leaves while drying and shaping, achieving integrated processing of drying, shaping, and antibacterial. Without the need for additional preservatives or secondary sterilization treatment, it can ensure the original ecological quality of leaves and significantly extend the storage period of finished products.
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