Manufacture Of Traditional Black Leaf Tea
There is a story in tea that is inspiring in its expression. It is a tale that starts with a tiny seedling which evolves through the influence of soil, rainfall, sunshine, temperature and the skill of the tea planter. Eventually it offers the tender green shoots of the now matured Camellia sinensis plant, which are then skillfully harvested by hand. The story spans thousands of hectares and millions of lives in Ceylon’s famous tea country, known as the home of the world’s finest tea.
Major brands have abandoned the traditional, centuries old method of making tea for a new “fast track” process, which sacrifices the character and taste of real tea. Dilmah remains faithful to traditional and authentic tea. That’s why Dilmah tea tastes so different.
TEA (Camellia sinensis)
Harvesting fresh young shoots from mature tea bushes is known as plucking. Each pluck picks only two tender leaves and bud of succulent fresh growth. Within seven to ten days the bushes grow new shoots. Plucking is traditionally done by skilled women, adept at picking the shoots, and throwing handfuls into the carrier baskets resting on their backs. In Ceylon’s temperate climate, tea is a perennial crop.
When tea leaves are plucked from the bushes, the moisture content is about 75%, and is then reduced to approximately 45%. The fresh leaf is spread out on withering troughs about a foot deep and a flow of cool air helps reduce moisture. This process can last from 8 to 18 hours depending on weather conditions. Significant chemical changes occur during withering. The cell membrane permeability is increased allowing for disruption of cell structure.
Withering is the most critical process in black tea manufacture. The primary aims of withering are to reduce the moisture content of the leaf and to soften it, so it becomes pliable and will withstand the subsequent process of ‘rolling’, without breaking up into flakes. Additionally, controlled moisture extraction from fresh leaf is required to activate a series of bio-chemical reactions. These enzymatic changes are ultimately responsible for the production of various biochemicals desired for achieving quality parameters in made tea.
Significant chemical changes occur during withering. The cell membrane permeability of the leaf is increased allowing for more disruption of cell structure. As a result, amino acids, caffeine, organic acid levels and polyphenolase activity is increased.
Rolling of the withered leaf was perfected over centuries, a process which brings out flavour in tea. Rolling assists in establishing proper conditions for enzymatic oxidisation of the flavanols by atmospheric oxygen. This is achieved by disruption of cell structure which facilitates enzyme substrate contact.
The purpose of rolling is to achieve the final curved appearance and to break the leaf cell walls so as to release essential oils to start a chemical reaction of fermentation. The leaf is rolled several times. The first roll, known as the pre-conditioning roll is very gentle, of which the aim is to cover the twisted particles with the juices from the leaf. The rolling process is what releases the colour, strength, aroma and the taste of the liquid we ultimately pour into our cups.
When the leaf cells are ruptured following the rolling of the withered leaf, the enzymes in the leaf come in to contact with the oxygen in the air which initiates chemical reactions that are necessary for the production of black tea.
Roll breaking has two primary objectives. To remove the twisted leaf off the rolled shoots that clogs and impedes circulation, and to facilitate further twisting action on the large leaf. Additionally, it also cools the leaf which would have risen in temperature during the process of rolling.
During fermentation, also known as Oxidisation, green leaf is converted to black tea. Although this is referred to as fermentation, it became recognised as oxidisation, a process initiated by the tea enzymes. This process starts at the onset of maceration during the rolling process, and it is allowed to continue under ambient conditions. The temperature of leaf is maintained at around 25-30 degrees. Mild acidification of the oxidised tea increases the levels of the tea theaflavins.
The finer particles collected after roll breaking are fermented to bring about the changes necessary to make a tea liquor palatable. This process can only take place when the cells of the tea leaf are properly ruptured. Here, in the coolness and darkness of the fermentation room, an oxidising enzyme produces brown products from the remaining water in the tannin. During this process, the green leaf is converted to black tea. Although this is referred to as fermentation it became recognised around 1901 as an oxidisation process initiated by the tea enzymes.
Firing & Baking
During this process, hot air is passed over the tea leaves to deactivate fermenting enzymes. Many organo-chemical processes are accelerated during this process, as are the enzymatic reactions before thermal inactivation. Firing also reduces the moisture level to 2-3%. This is critical as incomplete inactivation can cause accelerated deterioration of quality. There are several grades of tea, such as leaf grades, broken grades, fannings & dust grades.
The fermented leaf is dried to stop any further chemical reactions taking place. Passing hot forced air over the tea leaves deactivates fermenting enzymes. Many organo-chemical processes are accelerated during this period as are the enzymatic reactions before they are inactivated due to heat. Firing also reduces the moisture levels of the tea to 2 — 3%. This is critical as incomplete inactivation can accelerate deterioration of the tea during storage.
Sorting & Grading
Baked tea is sorted into different grades by passing them over a series of vibrating screens of different mesh sizes — lectrostatically charged rollers preferentially attract stalk and fiber to remove them from the tea.
The last operation in this long process of manufacture is the sorting and grading of the fired tea. Its importance cannot be overstated as it is here that the value of the final product is often determined.
GRADES OF TEA:
Green leaf from a single plantation is converted to various grades of tea in a common manufacturing process. These grades are:
Additionally, each of the above grades carry a sub-category denoted by the number one i.e. BOP1, BP1, OP1 and so on.
Since Tea originated in China, descriptions of tea leaf sizes may have been phonetically converted from Chinese to English. Hence, words like Orange Pekoe and Broken Orange Pekoe are strictly related to the size of leaf and not to the quality of tea. There is no orange taste or additives in Orange Pekoe or Broken Orange Pekoe.
Orange Pekoe for example, which is the largest, delivers a very light, mellow taste while Dust which is the smallest, delivers the strongest taste. Each grade has its own particular character.
Dilmah tea is packed at source in Sri Lanka within days of manufacture, and is therefore fresh and brimming with antioxidants.
Variations of the MANUFACTURING process to obtain White, Green and Oolong teas
White teas are entirely handmade. They are rolled by hand and dried in filtered sunlight. In Sri Lanka, white tea is referred to as Silver or Golden Tips. Green tea is not fermented. Fresh leaf, on arrival at the factory, is immediately treated under high temperature by steaming or baking. This deactivates the enzymes that cause fermentation. The oxidation of polyphenols cannot take place and are preserved. This is why green tea has its unique flavour.
In the case of Chinese green tea, the fermentation process is stopped by either exposing the leaves to sunlight or applying warm air to the leaves and then pan-firing the leaves to stop all further processes.
Oolong tea is semi-fermented. In essence, it follows a similar manufacturing process as black tea although the oxidation is for a very short time. Oolong tea is usually much darker than green tea and stronger in taste than green tea; but Oolong is lighter in colour than most black teas and usually has a more delicate taste.