When the development of tea production is examined, it is seen that it consists of five stages, from manual production to today's production with various mechanizations.
The first period is the production of handicrafts by Chinese peasants since 3000 BC. In this method, the tea leaves are left in a windy place and withered. Hand-kneaded and rolled leaves are oxidized by keeping them in a cool place. Afterwards, the teas dried on the metal sheets in the barbecue were sorted by hand. Manufacturing will be completed in about 3-5 days.
The second circuit is Assamese production, a simplified form of the Chinese style. All processes in this production are done by hand. The production, which consists of five stages, is completed in one day.
Orthodox manufacturing, which emerged with the introduction of mechanization, constitutes the third stage. All of the manual production in Chinese and Assamese methods has been done by machine since the 1840s and in this developing mechanization period.
The fourth stage is the production of C.T.C and Rotervane, which simplifies the difficult and time- consuming processes of orthodox manufacturing and develops with the introduction of new machines.
The fifth stage is the Continue system tea production, which minimizes the production time, operating costs and manpower with the completely uninterrupted operation of modern machines.
All tea producers and tasting experts agree that the best tea can be obtained by machine processing by the Chinese peasant, unchanged in principle. In our country, Çaykur and almost all of the private sector enterprises are made with different machines. Now let's examine the black tea production stages:
It is the phenomenon of reducing the u-80 humidity in fresh green tea leaves to `-65' with the help of the air environment. The cell sap of withered leaves condenses and gains flexibility suitable for the next process, rolling. If the leaves are coiled without wilting, breakage and chipping will increase. This situation, which causes the amount of powder in the finished tea to be excessive, reduces the commercial value of the tea. During the withering process, in addition to evaporation, the activity of the polyphenol oxidase enzyme in the leaf also increases. Wet tea leaves are withered in two ways, natural and artificial. In natural withering, wet tea leaves are laid on the crayfish exposed to normal airflow, and this process is carried out over a period of approximately 24 hours. Artificial withering is used in production processes to accelerate withering and not depend on the temperature and humidity of the outside air. The most applied system is the Traf method. Here, around 32°C air is given under the scissors and the tea leaves laid on the scissors are withered within 3-5 hours.Factors affecting withering:
- Leaf type
- State of the leaf
- Age tea collection standard
- Pave thickness
- Fading Period
- Drying capacity of air
The basis of the rolling process is the physical removal of cell sap from the cell vacuoles of withered green leaves and the oxidation of the polyphenol oxidase enzymes in the cell water by contact with air.
The work of the wrapping machines is similar to the work of taking the tea leaf between two palms and twisting it with circular movements. Below the rolling machine was a horizontal and fixed table, above which was a cylinder from which the withered leaves were fed. Withered leaves are gradually poured from this roller to the tray, and the leaves are bent by the movement of the tray and rollers. Since the leaves are also partially crushed and disintegrated during this process, the cell sap comes out and is oxidized with the help of polyphenol oxidase enzymes.
The curling process is repeated 3-5 times. At the end of each rolling, wet teas are sieved. While the parts that pass the sieve are left to oxidize, the parts that do not pass are given to the rolling again. The best quality tea is obtained under the sieve, which passes through the sieve in the first rolling, where the "bud" part of the tea sprout is located.
Factors affecting curling:
- Leaf type
- Leaf wilting rate
- Spin capacity and speed
- Degree and duration of pressure application
- Ambient and machine temperature
- Size of bent parts
- Curling drums, type, type, working principles
- Desired type of tea
It is the formation of new compounds by enzymatic and chemical reactions of polyphenols (catechins) found in tea leaves. In the curling of withered leaves, oxidation begins with the release of water-soluble polyphenols inside the cell. The curled leaves are laid in a separate place and left to oxidize for a certain period of time. Here the green leaves change color, become bright copper color and some aroma substances are formed.
Because the rolling is done several times and sifted each time, the oxidation of the curled leaves separated in the sieving will not be the same. Generally, the first sieved leaves oxidize quickly and the last sieved leaves oxidize late.
During production, the main changes in the leaf occur during oxidation, colorless polyphenols are oxidized to form colored compounds and thus the characteristic color of black tea infusion. The amount of theaflavin and thearubigens formed in oxidation depends on the amount of phenolic substances in the tea shoots, their properties, the oxidase activity of the shoots and the production method.
It has been observed that theaflavin amount is the factor affecting the taster in terms of brewing color tone, brightness and vitality. The amount of Tearubigen influences tasters' judgment about the intensity of the brew color. A very good correlation could be established between the judgments of tasters regarding these properties and the amounts of theaflavin and thearubigen obtained as a result of laboratory analyzes in black tea.
At the end of the oxidation, the teas acquire a vivid copper-red color, a bright appearance and an apple scent.
Factors affecting oxidation:
- Fermentation time
- fermentation temperature
- spreading thickness
- emitting density
- Oxidation unit conditions
- The way the leaf curls
- Genetic structure of the leaf
After completing the oxidation process, the tea leaves are dried at high temperature in a short time. Drying the leaves in a short time and at high temperature is to neutralize the enzymes that will stop the oxidation and make the tea durable. Tea drying ovens consist of 6 rows of bands moving from the upper part to the lower part.
The drying process in the oven is carried out according to the counter-current principle. Air at 100°C is supplied to the oven from the bottom. Oxidized tea entering the oven from the top encounters air at 50°C in the first band and at 70-80°C in the second band, which inactivates the enzymes. This is to prevent fresh leaves from being exposed to high temperatures at the start of the oven, preventing them from hardening and drying out completely.
Oven temperature does not rise above 100°C. In this way, the tea leaves gradually dry out and come out of the lower band. The moisture content of the tea coming out of the oven is around 3-4%.Factors that affect drying:
- dryer air temperature
- Flow rate of drying air
- Number of sheets or feed rate of the oven
- Drying time Inlet and outlet air temperatures
- Features of the furnace
5.Sorting and packing
During processing, the tea leaves are broken into particles of various sizes. Small parts are both more oxidized and contain less moisture at the end of the drying process. These differences in particle size and their consequences have a great influence on the character and quality of the tea. For this, it is necessary to sift this mixture and separate it into various sizes.