Tea withering machine consists and working principle

Tea withering machine consists of the frame, heat supply system and fans set.

It is characterized that in the heat supply system with a hot air duct axially seted in the cavity of the drum, the wall of the hot air duct is provided with air outlet holes, and the wall of the cavity of the said drum is provided with inclined stagger-distributed screw conveyance pieces and several axial distributed tea-turning plates. 

The collected green leaves are spread in a given thickness, and through air-drying they are under the withered state. During the withering process, the green leaves are subjected to a series of change: the moisture diminishes, the leaf becomes soft from brittle-hard to facilitate rolling and striping, the activity of the enzyme-containing substances increases, which promotes the decomposition and transformation of the green leaf ingredients (starch, protein and insoluble protopectin) to form effective substances advantageous to quality of finished tea (such as glucose, amino acid, and soluble protopectin), and somewhat oxidizes polyphenol-like substances. 

Normal and effective withering will remove grass aroma from green leaves and generate delicate fragrance and fruit or flower flavor, and the finished tea is full of pure elegance but is not bitter. The withering requires proper temperature, RH and air circulation. The first process in making Chinese white tea, black tea and Oolong tea is withering at different degree. The withering degree of the white tea is the highest, and the water content in the green leaf shall be lowered to below 40% , that of the black tea is secondary and the water content in the green leaf shall be lowered to about 60%, and that of the oolong tea is the lowest, and the water content in the green leaf shall be lowered to 68%-70%.