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Tea processing is a traditional industry in China. In order to improve the processing quality of tea and industrial modernization, microwave drying technology can be introduced. Microwave drying technology is a drying technology that intensifies the high-speed movement of water molecules inside the material structure and generates heat. The microwave penetrates into the material and interacts with the polar molecules of the material to be converted into heat energy. Microwave drying equipment has the advantages of rapid temperature rise, easy operation and time control, and is widely used in food, medicine and paper industry.The tea microwave dryer has great advantages in comparison with traditional drying equipment in sterilization, drying,storage and tea moisture determination.
First, the application of tea microwave dryer in tea sterilization
The application of microwave in tea sterilization is a key technical measure to form and improve the quality of green tea. The fresh leaves are sterilized by high temperature, completely destroying the activity of the enzyme, removing the grass gas from the fresh leaves, and evaporating a part of the water, laying a good foundation for ensuring and improving the quality of the green tea. So far, the sterilization technology often causes the tea to produce red stems, red stagnation, and uneven sterilization due to improper operation. Microwave technology is used for sterilization. Because the heat of the microwave is from the inside and the surface, it is easy to kill and kill, effectively avoiding the red stalks, sterilizing and other diseases.The experimental results show that the microwave sterilization heating time is short, only 1/3 of the traditional killing time, and the microwave sterilization leaf temperature is low, only need to rise to 58 °C to meet the sterilization requirements, 22 °C lower than the traditional method sterilization temperature, so The destruction of chlorophyll is greatly reduced, and the quality of sterilization is effectively improved.
Second, the application of tea microwave dryer in tea drying
Microwave drying, like traditional drying, is also based on the vapor pressure difference between the water inside and outside the object, which creates a driving force for moisture transfer. The conventional drying method requires a certain amount of time to conduct heat from the outside to the inside, and there is a problem that the temperature difference between the inside and the outside is opposite to the direction of the wet and heat transfer. Microwave heating can cause the surface and interior of the material to heat up at the same time, and the internal temperature is higher than the surface of the material, so that a large amount of water molecules escape from the material and are carried away by evaporation to achieve the purpose of drying. This drying method is characterized by a short heating time and a heat transfer direction which is consistent with the wet transfer direction. Therefore, the microwave dried tea product has less chlorophyll change, green color, uniform drying, less aroma loss, and the product quality is obviously superior to the tea dried by the conventional method. The research on the tea industry experimental field in Saitama Prefecture, Japan, found that the use of microwave drying can effectively improve the bad odor of bitter and astringent taste of green tea, and significantly improve the quality of tea.Experiments have also shown that microwave drying can maximize the nutritional content of tea, especially vitamin C. For example, in the same case, the ordinary heat-dried green tea has a vitamin C content of 171.6 mg 100 g, and the microwave-treated dry green tea vitamin C content is 428.6 mg 100 g.
Third, the application of tea microwave dryer in tea storage
At present, tea is mainly dispersed and produced and transported to the tea factory for tea processing through acquisition. Therefore, tea storage is inevitable. However, tea leaves often absorb moisture and mold and insects due to improper storage. Treating tea leaves with microwave can play a re-ignition effect, prevent mildew and insects of tea leaves, and destroy the activity of residual enzymes in tea leaves to stop enzyme oxidation, which can effectively improve the storability of tea leaves. Studies have shown that the storage period of tea is directly proportional to the intensity of microwave irradiation. Therefore, tea leaves with long storage period need to be treated with higher intensity microwave. However, the microwave intensity should not be too large, otherwise it will cause the tea to ignite.
Fourth, tea microwave dryer for the determination of tea moisture
Tea moisture is an important factor affecting the quality of tea, and it is also an important indicator for tea processing, acquisition and storage management. At present, the determination of tea moisture generally uses the oven method, which requires the tea sample to be baked in an oven for more than 2 hours. Although the measurement results are more accurate, the cycle is long and the energy consumption is large, which is difficult to popularize in the ordinary tea purchase department. Microwave has a good heating effect on water, high energy utilization rate, and can be completed in a few minutes by using microwave as a moisture analysis method. It is convenient, time-saving and economical, and can analyze several samples at the same time. However, the determination of the moisture content of tea leaves by microwave can not wait until the sample reaches a constant weight, but should be changed to a degree of no focus. The standard deviation determined by this method is significantly higher than the national standard method. Therefore, the national standard method should be implemented in strict quality inspection.
Application prospects of microwave drying
With the increasing application of microwave technology, the application of microwave in tea processing and deep processing products will have broad prospects. If the microwave drying equipment is used to dry the instant tea, the color, aroma and taste characteristics of the tea can be preserved to the utmost extent; the microwave can promote the high efficiency and strong selectivity of the reaction, and the operation is simple, the side reaction is small, the energy consumption is saved, The advantages of high yield have begun to be applied in the extraction of active ingredients of tea, such as extraction of tea polyphenols, extraction of tea pigments and extraction of tea juice, which can significantly increase the extraction rate, reduce costs and reduce pollution.
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