Tea fixation is also called deactivation of enzymes, kill out or de-enzyme. The main purpose of tea deactivation of enzyme is to maintain the color of tea green, volatile smell of green, alter tea soft texture and conveniently further rolling process. The finished tea after enzyme deactivation is green in color, better shaped and fresh in aroma

Using microwave radiation to de-enzyme tea is a new technology which can precisely control heating temperature and products quality. The specific heating feature can heat tea surface and internal at the same time resulting in tea internal temperature higher than the surface temperature which cause a lot of water molecules evaporated, so the green color is fixed. Microwave enzyme deactivation of tea leaves is characterized by short heating time, consistent internal and external temperatures. Comparing to conventional heating methods which transfers the heat from the external surface, it takes less time

The moisture content of the tea leaves after tea fixation should be 58-60%, and the moisture content should be 4-6% after final drying. The processed tea leaves should be kept original flavor, original texture and original colors. The nutrients should not be lost. The actual situation of tea leaves is that the physiological structure of tea leaves produced in different seasons will be different, and the moisture content and tenderness of the tissues are different, so the raw materials used for tea making are different. For example, when we harvest tea in April, the leaves are with tender organization and high moisture content, However, the summer and autumn leaves are with older organization. Fresh leaves produced in different seasons have different technological requirements for de-enzyme and drying, which brings certain difficulty for de-enzyme and drying equipment and technology. At present, the roasting process and hot air drying process of tea leaves are largely arbitrary, and the heating temperature of the equipment is difficult to control. In the process of processing, tea leaves easily produce red stalks, red leaves, brown yellow leaves, uneven color and other unexpected phenomena result in the quality of tea leaves cannot be guaranteed. However, microwave has penetrating and non-thermal effect, which can rapidly heat up to the required temperature for killing green tea and drying, destroy the activity of enzymes in fresh leaves and prevent enzymatic reaction, which can solve a series of problems existing in traditional process.

At present, the microwave dryer is mainly used in the processing of high quality green tea product, and it is a relatively mature technology. Microwave model includes box oven microwave equipment and conveyor microwave equipment. The specific choice of equipment depends on the shape, quantity and processing requirements of materials. For example, in order to obtain uniform heating when the product needs to be continuously produced in the assembly line, the conveyor belt can meet with demands. For small batch production or laboratory sampling materials, a single microwave heating box oven can be used. In the design of tea microwave heating equipment, the biological and physical characteristics of the tea, as well as some related factors in the processing, operation and maintenance of the equipment should be taken into comprehensive consideration according to the characteristics of each microwave. The continuous flow-line microwave equipment is more suitable as the basic design model. It has the following advantages:

1. It is easy to determine the heating and drying process of tea, and the microwave power can be adjusted as required within the set range.

2. Simplified equipment design, combined installation, convenient processing, transportation and maintenance. We could produce both small quantity and large quantity.

In tea microwave tea process, we found that different seasons sea has a different moisture content. In order to meet the needs of different water content of spring, summer and autumn tea, the process of killing green tea with different degrees of aging and tenderness, a set of water adding device is able to address. When the water content of processed tea is low and old, certain amount of water is appropriately added, which can greatly improve the quality of processed tea.

The surface temperature and humidity of the tea processed by microwave equipment are still high when we collect the tea in the end of machine. If the tea cannot be quickly cooled and dehumidified, the color and quality of the tea would be easily affected. In order to solve this problem, a cooling system can be set up at the exit of the machine.