Tea types & processing
There are six categories of tea: white, green, yellow, oolong, black, and dark (pu-erh is a dark tea). The different types are categorised by the level of oxidisation or fermentation that takes place during the processing of the leaves and buds with white tea being the least oxidised and black being the most.
Oxidation is what happens when the juices in the tea leaves react with oxygen in the air around them. As this happens, the leaves turn from green to brown. It’s exactly the same process that happens if you cut an apple or a pear and watch the flesh of the fruit turn from white to brown as it oxidises. The longer the leaves are allowed to oxidise the browner they will become and, when the tea is actually brewed, the darker the liquor will be.
Black teas are 100% oxidised. We make oxidation happen by breaking or cutting the tea leaves.
To make black tea, the freshly-picked leaves are allowed to wither for 18-20 hours to evaporate 30-35% of the water content. Next the leaves are rolled or cut to break the cells and provoke oxidation.
There are two different methods of rupturing the leaf cells.
The ‘orthodox’ method is the traditional way in which tea is rolled by hand or machine. This rolling breaks and twists the leaf, rupturing the cells and causing the juices to come to the surface and react with oxygen. This style of manufacture gives large, medium and very small pieces of leaf.
The CTC (cut, tear, curl) method was invented in the 1930s to make small particles of tea for teabags. Smaller particles brew faster and give greater colour and strength more quickly and so are perfect to put inside paper teabags.
Once the leaves have been rolled or cut, they are allowed to oxidise until the leaves have turned dark brown. To stop any further oxidation and to remove most of the remaining water content, they leaves are put into hot ovens for drying.
Green teas are not oxidised at all. We intervene during processing to stop any oxidation.
When we make green tea, we try to capture the green colour and the green character of the leaves. So we must stop all natural oxidation from taking place in the leaves and leaf buds. This is done by applying heat (dry heat, called panning, or steam) which kills the enzymes that would otherwise have allowed oxidation to take place. This application of heat is called ‘de-enzyming the leaf’ or ‘fixing the green’.
Once the leaves have been picked, they are panned or steamed to de-enzyme them, rolled or pressed (to develop the flavour), and then dried. The water content remaining in the leaves is approximately 2-3%.how long does process take?
The way in which the leaves and buds are rolled gives the leaves a particular appearance. For example, Long Jing green tea is pressed by hand into little flat needles in a wok, gunpowder is rolled by hand or machine into little pellets, Mao Jian is rolled by hand on bamboo baskets and so looks lightly curved or twisted.
Oolong is the most complicated tea to produce requiring great skill, experience and time to create the range of flavours, fragrances and liquor colours that make this tea so special.
‘Oolong’ means ‘black dragon’ and the name comes from traditional oolongs which have large, twisted dark brown or black leaves that can look exactly like dragons or serpents.
Oolong teas are partially oxidised, on a scale between approximately 20% and 70%. The tea maker can control the level of oxidation that takes place during manufacture.
There are two main types of oolong:
- Dark brown open-leafed oolongs that have been allowed to oxidise up to 70%;
- Green balled oolongs in the shape of tight pellets that have been allowed to oxidise to 20-30%.
To make the darker type of oolong, the freshly-picked leaves are allowed to wither in sunlight for about 2 hours. During this process light oxidation begins to take place. The leaves are taken indoors where they are shaken and tumbled in a bamboo drum to lightly bruise the leaves after which they are spread on bamboo baskets and left to oxidise up to 70%. To stop oxidation they are panned, rolled to develop the flavour and then dried.
To make the green, balled oolongs, the freshly-picked leaves are allowed to wither in sunlight for about 2 hours. They are then taken indoors, shaken and tumbled and allowed to oxidise up to 20-30%. They are then panned (to stop any further oxidation) and rolled. Finally they are put inside cotton bags and tightly rolled and squeezed to form tight jade-green pellets before being dried.
Pu-erh tea is a dark tea from China’s Yunnan province. Pu-erh is the name of the market town where these teas have been bought and sold for hundreds of years.
Dark teas start as green teas and then go through a secondary aging process during which the character of the tea slowly changes. This is caused by micro-flora, bacteria, yeasts, penicillin, microbes and so on in the tea. This secondary, post-production process, causes fermentation as well as oxidation.
To make Pu-erh tea, a green tea is made from the leaves and buds of the local Camellia sinensis var. assamica found locally in the mountains of southern Yunnan This green tea is called ‘maocha’ meaning “light green rough tea” or “crude tea” and was created as a low budget tea. It is made by panning, rolling and drying the leaves in the sun.
The tea is then steamed or dampened, compressed into cakes or left loose, and allowed to age in temperature-controlled and humidity-controlled conditions for several years.
White teas always go through very light natural oxidation
The finest white teas are picked early in the spring before the leaf buds have opened and whilst they are still covered with silky white hair. When we make white tea we try not to cause any oxidisation to take place and so it is really important that the pickers use the utmost care to avoid damaging the cells of the leaves and buds which, when broken or bruised, start to oxidise.
Once picked the leaf buds and leaves are spread on bamboo baskets or mats and are left to wither and dry in the sun. Then, they are withered and dried on bamboo baskets indoors. The water content remaining in the leaves is reduced to 2-3%.
There is always a certain amount of very light natural oxidation in white teas but we don’t do anything to cause it or to stop it. It’s a totally natural process making white teas the purest of all teas.
Yellow teas go through a light oxidation stage to mellow and smooth the flavour.
To make yellow tea, the leaves are panned to de-enzyme them, then while still warm and damp, they are wrapped or heaped and left for 2-3 days. Then they are panned again and then re-wrapped or heaped and left for 3-4 days. Then they are panned for a third time to remove most of the remaining water in the leaves. The water content remaining in the leaves is reduced to 2-3%.
The wrapping or heaping stages hold water and warmth in the tea and these cause light oxidation to take place giving the tea a smoother mellower character than green tea has.