Tea Production

The Plant
The tea plant (Camellia sinensis) is a species of tree related to the camellia. Its flowers are yellow-white and its fruits small and hard-shelled, similar to a hazelnut. The evergreen leaves are leathery, dark and slightly serrated. Given minimum annual temperatures of 18 C, moderate and infrequent frosts, a uniform annual precipitation of 1600 and a good balance of sunshine, a tea plant can easily grow to become 100 years old. Wild tea plants are indeed reputed to reach an age of up to 1,700 years.

 

Tea contains
Cafferin (teine)/Tannins/Amino acids/Proteins
Trace elements and minerals: fluoride, potassium, calcium, manganese/Vitamins: niacin, vitamin B1 and B2

“Tea both stimulates and calms”: Tea owes its stimulatory effect to its caffeine (teine) content: It does not act on the circulation via the heart, however, but directly on the brain and central nervous system, as it is bonded to the tannins and is not released until it reaches the intestine. This explains the demonstrable capacity of tea to increase concentration and responsiveness.

In the Island of Sri Lanka, tea is produced in three elevational cultivation areas of High grown, Medium grown and Low grown which has become famous throughout the world. Sri Lanka is the only country within the tea growing nations which manufactures all type of teas which include CTC, Rotorvane, Orthodox and Green Tea.

Tea Cultivation
Tea bushes require regular pruning to prevent flowering and fruit formation. This also makes it easier for the tea pickers to gather the two uppermost leaves and the newest bud (only these are relevant for the tea harvest). Most picking is still done by hand in order to preserve the quality of the harvest. Some countries have developed mechanical picking methods, however, which greatly simplify production processes.

The Orthodox Production Method
This production method consists of five stages – withering, rolling, fermentation, drying and sorting.

Withering
The freshly picked green leaves are spread out to dry on ventilated trays. During this process, approximately 63% moisture is extracted from the leaves, making them soft and pliable for further processing.

Rolling
The leaves are then rolled by applying mechanical pressure to break up the cells and extract the cell sap. After 30 minutes, the leaves, still damp from the sap, are sieved to separate the finer leaves. These are spread out immediately for fermentation, while the remaining coarse leaves are rolled for a further 30 minutes under higher pressure. If necessary, this process is repeated several times. A short rolling time produces larger leaf grades, while longer rolling breaks the leaves up more resulting in smaller grades. During the rolling process, the cell sap runs out and reacts with oxygen, thus triggering the fermentation process. At the same time, the essential oils responsible for the aroma are released.

Fermentation
After rolling, the tea is spread out in layers approximately 10cm high for one to three hours in a cool, damp atmosphere to finish off the fermentation process. During this process, the substances contained in the cell sap oxidise. In this production phase, the green leaf gradually turns a copper colour. The colour and typical odour tell the person supervising the process how far the fermentation has progressed. Various chemical reactions cause the leaf to heat up during fermentation. It is critical for the quality of the tea that the fermentation process be interrupted at its peak, when the temperature is at its highest.

Drying
Next, the tea is dried with hot air at a temperature of approx. 850°C to 880°C in order to interrupt the oxidation process. The residual moisture is thereby extracted from the leaves, the extracted sap dries on the leaf and the copper-coloured leaf turns dark brown to black.

Sorting
Finally, the dried tea is sieved to separate the different leaf grades. The orthodox production method provides teas of all leaf grades: leaf, broken, fannings and dust. Leaf grades only refer to the leaf size; however, they are not necessarily an indication of the quality of the tea.

The Production of Green Tea
Green tea comes from the same plant as black tea, but the fermentation process is prevented by heat treatment immediately after withering.

Withering
This process is only carried out where necessary. The necessity and duration of withering varies widely according to the desired type of tea.

Steaming/dry heat treatment
This destroys the plant’s own enzymes so that the leaf will retain its green colour instead of turning “black”.

Rolling
Rolling is performed manually or by machine depending on the type of tea. In some cases the leaf is rolled into artistic shapes following a tradition which dates back thousands of years.

Drying
For this purpose, the leaves are either stacked in hot-air rack driers or exposed to the natural heat of the sun.

Sorting
Green tea is available in the same familiar grades – leaf, broken, fannings or dust – as black tea, depending on the production specification. Green tea is a strongly alkaline drink which protects the body from hyperacidity. It contains numerous tannins, minerals and vitamins.

The Rotorvane Production Method

Withering
The leaf is withered for a minimum of 12 hours with a percentage ranging 42% to 47% depending on the climate condition and the type of teas.

Rolling/Rotorvane/Dhool/Fermentation/Extraction
The leaf is rolled initially for a period of 30 minutes by applying pressure. Thereafter the rolled leaf is charged through a 12” Rotorvane and then double passed through an 8” Rotorvane. The first dhool is extracted (finer particles) through the rolled breaker fitted with No. 7 and 8 measures. The extracted dhool is immediately spread on fermentation beds. The balance bulk tea is once again passed through a conveyor and is fed to another set of 8” Rotorvane for further maceration. The second dhool is extracted on the same type of roll breaker with the same mesh numbers. The second dhool is again sent for fermentation and kept separately. The same procedure of Rotorvane cut and roll breaking, and the extracting of finer dhool, is continued till such time the final bulk is reduced to 2% to 3%. The fermentation period varies from 45 minutes to 3 hours depending on the climate condition and the type of teas. The fermenting area is separately identified with humidifiers surrounding the area to control hygrometric differences.

Drying
Next, the tea is passed through a dryer where hot air is circulated at a temperature between 2500°F to 2600°F. Finally the black tea is obtained from the dryer with an approximate run through period of 18 to 21 minutes.

Sorting
10 to 15 minutes after firing the tea is passed through a stalk extractor and thereafter through a fibre extractor to extract whatever possible stalk and fibre from the black tea whilst the warmth is maintained in the fired dhools. This operation is undertaken in the drier room itself to maintain the warmth in the machines and therefore extract as much stalk and fibre as possible. The fired tea is then passed through a Middleton sorter to differentiate larger particles and smaller particles.

After different shading of the two types of particles, it passes through separately on to a Chota sifter for grading purposes. This sifter has 5 numbers of different measures to extract graded teas, such as Pekoe, BOP, BOPF, Dust-1, etc. The graded teas are subsequently transferred in to bins which are located in the sifting room. These bins are air-tight and lined with aluminium sheets to maintain the freshness of the graded tea. Almost all factories in Sri Lanka are equipped with bulkers to bulk the graded teas prior to packing.

Once the teas are packed in to tea sacks these are stacked in the factory compound itself. The ex-estate catalogued teas are retained on the estate till such time the teas are sold at the Colombo auctions. The cataloguing and selling of teas takes approximately three weeks from the time of packing the teas. Once the teas are packed, off grades and dust grades are sent to brokers’ warehouses, where samples are drawn by the brokers and the teas are catalogued.

The CTC Production Method

CTC stands for crushing, tearing and curling. Both the CTC and LTP methods are mainly used for the finer end of the scale, i.e. fanning and dust grades. These teas are usually destined for teabag production. The withered leaf is often cut to a uniform size by machine. Then the leaves are fed into the CTC machine where they are crushed, torn and curled in a single operation by metal rollers. The extracted cell sap is collected and added to the leaves again. The crushed leaves are then fermented, dried and sorted.

The LP Method
The third method of producing black tea is the LTP method, named after the inventor of the relevant machine, the Lawrie Tea Processor. In this method, the withered leaves are often levelled before being processed in the LTP machine. Here they are virtually torn to pieces by blades rotating at high speed. This is followed by the usual fermentation, drying and sorting procedures.

About F&W

Forbes & Walker was set up in 1881 as a partnership between James Forbes and Chapmen Walker. Although there is no actual record of the date on which it was established the very first cash book, still in the possession of the Finance Director, indicates the brokerages were earned from 1st August 1881. In Sir Thomas Villiers' book “Mercantile Lore” the date of establishment of Forbes & Walker has been put down      Read More...

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