Manufacturing technology of black tea

Black tea in China includes Kongfu black tea, black broken tea and small black tea, and their preparation methods are more or less the same, with four processes: withering, rolling, fermentation and drying. The quality of all kinds of black tea is characterized by red soup and red leaves, and the formation of color and aroma has a similar chemical change process, but there are differences in the condition and degree of change. Taking Gongfu black tea as an example, this paper briefly introduces the manufacturing technology of black tea.

(1) withering

Withering refers to the process in which fresh leaves lose water for a period of time and make certain hard and brittle stem leaves wilt and wither. It is the first process of black tea production. After withering, the water can be evaporated properly, and the leaf is soft, toughness is enhanced, and it is easy to shape. In addition, this process and the disappearance of the smell of grass and the fragrance of tea is an important processing stage for the formation of black tea aroma. There are two methods of withering: natural withering and withering trough withering. Natural withering means that the tea is spread thin indoors or outdoors where the sun is not very strong, and leave it for a certain period of time. Withering trough withering is to put fresh leaves in the ventilation tank and pass through hot air to speed up the withering process, which is a commonly used withering method at present.

(2) kneading

The purpose of rolling black tea is the same as that of green tea. Tea forms and enhances the concentration of color and aroma in the process of rolling. At the same time, due to the destruction of leaf cells, it is easy to carry out the necessary oxidation under the action of enzymes, which is conducive to the smooth progress of fermentation.

(3) fermentation

Fermentation is a unique stage in the production of black tea. after fermentation, the leaf color changes from green to red, forming the quality characteristics of black tea black leaf red soup. The mechanism is that under the action of leaf kneading, the structure of tissue cell membrane is destroyed, and the permeability increases, which makes polyphenols fully contact with oxidase, produces oxidative polymerization under the action of enzyme, and other chemical components change profoundly accordingly. Make the green tea red, forming the color, aroma and quality of black tea. At present, the fermentation machine is widely used to control the temperature and time for fermentation. The fermentation is moderate, the color of the young leaves is red and uniform, the old leaves are red and green, the green grass gas disappears, and it has ripe fruit aroma.

(4) drying

Drying is a process in which the fermented tea blanks are baked at high temperature to quickly evaporate moisture and achieve quality dryness. It has three purposes: to use high temperature to quickly passivate the activity of the enzyme to stop fermentation; to evaporate water, reduce the volume, fix the shape, maintain dryness to prevent mildew, emit most of the low boiling point grass odor, intensify and retain the high boiling point aromatic substances, and get the unique sweetness of black tea.