Processing Tea

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The flavour and quality of tea depends on its variety, on the soil and climate where it is grown. Fresh tea leaves are mildly astringent and stimulating to chew. They are processed in three ways - for green tea, for oolong tea, and for black tea.

Tea Processing Equipment

The sheer volume of tea being produced in India required a colossal labour force and the greatest revolution in the tea industry was the invention of machines to process the freshly picked leaves. In 1870, the Jackson Brothers designed the first steam driven rolling machines, which were established by the long-established English firm of Marshall & Son. Until then, all the rolling, sifting, grading and drying of leaves had been done by hand, and the tea chests were packed down barefoot. The new machines, as well as freeing thousands from menial tasks and increasing output, also standardised methods of production. Tea could now be picked, processed and packed efficiently, ensuring maximum output and consistent quality.

Tea Processing

Withering

The first stage of processing is called withering. The fleshy green tea leaves are laid on huge trays and dried with hot air (25 - 30°C; 77 - 86oF) to reduce excess moisture by ⅓ to ½, which takes 10 - 16 hours[1][2]. These dried tea leaves are then rolled in a large rotary drum, breaking up the leaves and releasing the natural enzymes which start fermentation (oxidation), which takes 3 - 4 hours. At this stage, the leaves start to lose their green colour, turning the more familiar coppery brown known as Orange Pekoe (or orange coloured leaf). As the skilfully-controlled fermentation process continues, it is stopped by drying before the leaves become too black and plain, then the tea leaves are rolled into tight twists and graded.

Black teas

There are two methods of processing black teas[3]:

  • The traditional way, known as Orthodox Teas, keeps the look of the leaf whatever its size and is used for all China, Darjeeling and most Ceylon and about 10% of Assam teas.
  • In the modern manufactured method, the leaf is Crushed, Torn and Curled (hence CTC Teas) rather than rolled, producing strong black balls of tea which release a very strong flavour and colour. It is ideal for small, strong leaf teas which are needed to flow easily through packing and teabag machines.

Oolong and green teas

Green teas & oolongs are non-fermented teas that use orthodox methods - the tea leaves are picked and allowed to dry in the sun in bamboo baskets for a few hours, so inactivating enzymes and preventing oxidation. The tea leaves are then pan-roasted and finally rolled into attractive shapes that provide pleasure from the leaf before, during, and after the tea is brewed. These tea leaves range from bright to dull green and are pliable.

In Japan, green tea is steamed and processed into different forms, including powdered green tea or matcha, which is still used today in Japanese tea ceremonies. In Japan, there are 3 grades of green tea: bancha, sencha, and gyokuro. Bancha tea is Japan's ordinary green tea. It comes from the late summer pickings and is somewhat coarse in flavour and appearance. Sencha is one step up and comes from the first or second flushes. The tea is steam-fired, basket-dried and finally hand-rolled[4]. This process is more costly. Sencha gives off a grassy aroma and is pale in colour. Gyokuro tea is harvested once a year and only the bud and tiny first leaf are plucked. This process means precious dew. This tea brews to give a very pale green to yellow colour and has a clean brisk flavour.

Oolong teas are semi-fermented, partially withered and partially oxidised. China and Taiwan are the main producers of this type of tea. Leaves for oolong must be picked at exactly the right time and processed immediately afterwards. They are withered in direct sunlight, then shaken in bamboo baskets to bruise the edges of the leaves which turn a reddish-brown colour after oxidation has occurred[5][6]. This process is repeated a few times. Oolong tea leaves are never broken by rolling as in green teas or by machines with black tea, and they should always be long and whole leaves.

References

  1. Encyclopaedia Britannica (undated) Withering, Encyclopaedia Britannica (accessed 31 May 2016) [1]
  2. Gebely, T. (undated) What is Withering?, World of Tea, 12 February 2012 (accessed 31 May 2016) [2]
  3. Cargill, A.C. (undated) The orthodox vs CTC tea debate, Lochan Tea (accessed 31 May 2016) [3]
  4. ITO EN (undated) The processing of green sencha tea (accessed 31 May 2016) [4]
  5. Tea from Taiwan (undated) Processing oolong tea (accessed 31 May 2016) [5]
  6. TeaGoodness, R. (undated) Oolong Tea: covering the basics, TeaMuse (accessed 31 May 2016) [6]

Further Reading

  • Gascoyne, K., Marchand, F., Desharnais, J., Américi, H. (2014) Tea: History Terroirs Varieties, Ontario, Canada, Firefly Books. ISBN 9781770853195.