Application of microwave equipment in the field of tea fixing and drying

After years of exploration and research on microwave equipment, significant breakthroughs have been made in the application of microwaves in the field of tea fixing and drying. This has provided feasible ideas for improving the processing quality of tea and modernizing the industry with microwave equipment. It is expected that microwave technology will have a promising application in tea processing.

In the application of microwaves in tea leaf fixing, microwave heating is used for rapid fixing treatment to inactivate the activity of polyphenol oxidase, evaporate some water, volatilize the grassy smell, and soften the tissue. Currently, the commonly used method for fixing in production is pan-firing, with a few places adopting steam fixing. Experimental results show that the quality of tea processed by microwave fixing and pan-firing is good, and there is no significant difference in microwave equipment. However, microwave fixing takes a shorter time (1/8 of the pan-firing time) and can be carried out continuously. Due to the high moisture content in steam, the outer layer of the raw material is affected by high temperatures, resulting in almost no weight loss of the fixed tea leaves, some chlorophyll is damaged, and the nutrients contained in the raw material are partially lost with the condensed water, making the quality less ideal. The application of microwaves in tea leaf fixing is mainly due to its thermal effect. When the magnetron generates microwaves and irradiates the tea leaves, the polar molecules inside the tea leaves are affected by the periodic changes of the microwaves and undergo periodic activity along with the microwaves. Due to the high frequency of microwaves, the internal molecules of the tea leaves collide at high speeds, generating a large amount of frictional heat that rapidly increases the temperature of the material, thus achieving a rapid temperature rise effect.

The application of microwaves in tea drying typically involves external heating during hot-air drying, where the surface dries while heat transfers inward, in a direction opposite to that of moisture diffusion, hindering the evaporation of moisture. Microwaves, on the other hand, provide internal heating, causing parts with high moisture content to heat up faster. Therefore, in microwave drying, moisture migrates from the inner layer to the outer layer at a faster rate, significantly speeding up the drying process compared to hot-air drying. The application of microwave drying in tea drying offers several advantages: fast drying speed; good product quality; due to the lower surface temperature of tea leaves, there is less change in chlorophyll content, resulting in a green and vibrant color that is resistant to storage and with minimal aroma loss; the drying is uniform with microwave equipment; and because moisture evaporates quickly, it is easy to form porous structures, leading to good rehydration properties of the product, making the contents easier to dissolve when brewing tea. Microwaved tea can improve the quality of tea by one to two levels based on traditional techniques.