Processing Indian Black Teas

Processing Indian Black Teas

In order to compete with the low production costs of the Chinese, who had access to a very cheap labor force, the British had to reinvent every stage of processing. They needed to reduce costs by turning their tea plantations into industrial enterprises.

As we have seen, the first methods of processing black tea appeared in China during the 17th century. To produce satisfactory results, this method required the repetition of numerous steps. The British were able to develop techniques that were far simpler and more efficient by mechanizing the whole process. Taking inspiration from Chinese traditional methods, at the end of the 19th century they created the first industrial technique, the orthodox process. This mechanized process requires expertise and intuition and allows for greater control over the different variables that affect the chemistry of tea leaves. This process is still used today to produce extremely high-quality teas, such as those from Darjeeling.


Developed by the British in northeastern India around 1860 and constantly improved upon since, the orthodox method is one of the oldest mechanized methods of black-tea processing. It consists of five steps: withering, rolling, oxidation, dehydration and sorting. More complex than the CTC method, the orthodox method is used to process the best black-tea harvests.


Withering reduces the water content of the leaves, softening them and changing the waxy texture so they can then be rolled without breaking. While dehydration changes the physical structure of the leaves, the natural activity of the enzymes begins to subtly change the chemistry of their flavors. This triggers, among other reactions, an increase in amino acids. The freshly picked leaves are evenly spread out in. withering vats on metal, jute or plastic grids that allow air to circulate freely. The ambient humidity; ventilation and temperature are constantly monitored to ensure successful withering. After 14 to 17 hours, the moisture content of the leaves will have been reduced by 60 percent to 70 percent.


The following stage, rolling, consists of breaking the outside membranes of the leaves in order to release the oils and enzymes they contain. For 10 to 20 minutes, the piles of leaves are held in copper vats inside enormous machines. These machines roll the leaves under pressure until they form a compact mass. Next, with the aid of a rolling machine, various levels of pressure are applied to the leaves following a precise cycle until their cellular membranes are broken, releasing the oils they contain. As soon as these oils are exposed to the air the phenomenon of oxidation begins. If rolling is too intense, the leaves will be discolored and dull, and if rolling is too light the leaves will be dry, gray and dusty and brew into a pale and tasteless liquid.


On contact with oxygen, the enzymes contained in the oils of the leaves trigger a chemical reaction called "enzymatic oxidation" or fermentation. This process of chemical change will determine the flavor strength, body and color of the tea.

The rolled leaves are spread out on trays made of stainless steel, ceramic or glass in a humid environment and at a temperature between 68 and 86°F (20 to 30°C). Depending on the moisture content of the leaves, they will be spread in a thin layer (for quick oxidation at low temperature) or in a thick layer (for slower oxidation). The temperature and humidity are sometimes controlled by humidifiers in order to maintain a minimum of 90 percent humidity in the room. Oxidation time can vary considerably, according to the ambient temperature and the type of tea being produced. While 15 to 30 minutes can be enough for First Flush Darjeeling teas, certain teas from the Assam region need to oxidize for up to four hours. This is a critical stage .and requires workers with expertise and good intuition because they must strike a perfect balance for the different tea flavors. Excessive oxidation will result in a liquid that is thick, strong and has a wine-like (fermented) taste, while too little oxidation will produce a green and raw infusion with a thin liquid. Often, in order to make the process easier to manage, the oxidation is slowed down to prolong the period during which the aromas are at their peak. According to many factory managers, this moment is recognizable by a surprising and very specific smell of apple. When the precise moment to stop the oxidation arrives, the leaves are ready to be dried.


Dehydration puts an end to the process of oxidation by altering the enzymes that causes it. The leaves are placed either on conveyors or on a series of revolving trays in a large machine that is heated to a temperature of 248°F (120°C). If drying is incomplete the oxidation process can continue uncontrolled, while if it is too intense the leaves will burn and acquire a smoky taste. The process lasts 20 to 30 minutes, until the moisture content of the leaves is reduced to 2 percent to 6 percent.


After the drying stage, the leaves are sorted. Vibrating grids of varying sizes placed one on top of another separate the leaves into different grades. The largest leaves remain on the top grid while the crushed leaves (fannings) and dust fall to the ground. The intermediate leaves are caught by the other grids.

In Darjeeling, all teas, regardless of the quality, are sorted in this way. The grade a tea is given is therefore an indication of size, not quality. Sorting is, however, an essential step, as each size of leaf requires a different infusion time and will have different characteristics.


The method of processing called CTC, which stands for crushing, tearing and curling, is an industrial method that was developed in India by Sir William McKercher . In the 1930s, borrowing ideas from existing machinery, Sir William perfected a system of industrial processing that would speed up the oxidation process and produce higher yields more quickly.

The CTC method consists of three simple steps. After a brief withering process, the leaves are cut and then crushed in metallic cylinders equipped with blades. During the next step they are tom apart by a machine called a Rotorvane. Finally, the leaves are sent to a ghoogi, a large barrel in which they are rolled into small beads.

At first used only for coarser leaves, this method gained in popularity in the middle of the 20th century, with the invention of tea bags. Although this method thoroughly revolutionized the tea industry, it was inevitably at the expense of quality. Furthermore, the majority of the leaves used in the CTC method are of an inferior picking quality.

Most tea-growing regions have adopted modern and highly mechanized production methods that aim for high volume and uniform quality. Hence, this method of production of black teas is now found in practically every country that produces high volumes of tea.


After picking, the harvest must immediately be sent to the processing plant to be treated in order to bring out its specific flavor. If the leaves are left to stand for too long they will become oxidized and unusable. Therefore, nearly every garden has its own processing plant. In Darjeeling, growers identify each daily harvest taken from their garden by a lot number. For example, the appellation "Darjeeling Singell First Flush DJ2" means that the tea comes from the second lot or "invoice" number processed during the first spring picking in the Singell garden of Darjeeling. It should be noted that a lot might come from just one section of a garden or be composed of a grouping from two or three sections.


When tea leaves the factory, the aromas of the first harvests are not yet completely stabilized. Growers will even maintain sufficient moisture in the leaves for a slight oxidation to continue, creating a process called mellowing. Thus, the tea will continue to develop over a period of up to three months after processing, after which the reaction will gradually stop. Some enthusiasts are passionate about the green aspect of the immature leaves and the floral character of the aromas reminiscent of muscat grapes, while others prefer the moment when the aromas are stabilized and the liquid acquires its full roundness.


There are three major systems of grading black teas. The grades refer more to the state of the leaves (whole, broken or crushed) than to their taste qualities. Usually, whole leaves will result in a more complex and aromatic infusion, whereas broken leaves create a darker liquid with a simpler flavor profile.

Here is the grading system used in Darjeeling to indicate the grade of a whole-leaf tea. In this case, the most important aspect is the number of buds (pekoes). The more buds a tea contains, the more letters there are in its appellation.

SFTGFOP: Special Finest Tippy Golden Flowery Orange Pekoe
FTGFOP: FinestTippy Golden Flowery Orange Pekoe
GFOP: Tippy Golden Flowery Orange Pekoe
GFOP: Golden Flowery Orange Pekoe
FOP: Flowery Orange Pekoe
OP: Orange Pekoe

Tippy refers to the abundance of flowering buds.
Golden refers to the tips that turn golden after oxidation.
Flowery refers to the slightly floral aroma released by the buds.
Orange is a purely historic reference to the Dutch royal family of Holland-Nassau, who were among the first to import tea into Europe.
Pekoe comes from pak-ho, meaning "white down." Also used to describe the hair of newborn babies, here it refers to the final leaf on a branch (final bud), which is covered in a fine white down.

The numeral 1 sometimes appears at the end of the grade of certain batches. Like the letter S, the garden manager adds the number one if he considers the batch to be exceptional.


Some experienced growers will test new processing techniques to obtain teas with different aromatic characteristics. By reducing oxidation time, they have developed teas that are clearer and lighter and contain greener leaves. This has led to the creation of wulong teas from fall harvests and to teas with floral aromas from the first harvests.