There are many ways to understand and categorize a tea: the choice of cultivar, the leaf varietal, the type, the style, the colour! But the most popular way of identifying a tea is by examining the processing techniques a leaf has been subjected to.
Tea processing techniques are what determine the final type of tea that you end up buying – the black, the green and the whole range in between. Of the 6 typical steps involved in making tea, inclusion or exclusion of steps results in particular types of teas. In this post, we will take you the steps involved in making tea and the what each of it contributes to.
Know your teas
It is possible to derive six types of tea – the green tea, the white, the yellow, the oolong, the black tea, and in some cases the post-fermented tea – from just one tea plant, the Camellia Sinensis. Each tea type can be further categorized by their ‘styles’ which result from modifications in one or more processing methods. A producer is capable of making different styles of the same tea type if they choose, say, a different tea plant, tea plant from a different appellation or a unique cultivar. But the most distinctive styles of tea emerge from unique intents of the tea maker!
Tea processing techniques
Typically, it takes anywhere between 2 to 7 steps to process fresh tea leaves; the addition or exclusion of some resulting in a particular type of tea. Each of the steps involved is carried out in a climate-controlled facility that helps prevent spoilage due to excess moisture, changing temperatures, and undesirable air particles.
Withering is the first step in making any tea. It refers to the wilting of the fresh green leaves, induced naturally or by application of dry heat. Wilting reduces the moisture content in the fresh leaves, which in turn allows the volatile flavour compounds in the leaves to concentrate.
Wilting typically takes places indoors and on rows of long perforated trough tables. Heat is passed under the tables, which forces the moisture out. During withering, which typically lasts 20-24 hours, the moisture content in the leaves drops down to about 30%. The leaves also turn soft, dark, and limp-looking. A short wither, however, allows the leaves to retain much of their green attributes and also a raw, green taste.
Fixing, also referred to as ‘kill-green,’ is the process by which enzymatic browning of the wilted leaves is controlled by application of heat – dry or wet. Fixing ensures that the leaves do not oxidise any more than desired, or in other words, turn ‘too brown.’ Typically undertaken when making green tea and oolongs, fixing follows a short wither, and with the intention of ensuring that the leaf retains some of it’s ‘green’ attributes and flavours.
Fixing takes anywhere from few seconds to few minutes. But the gentler the process of application of heat, softer and more fragrant the flavours in the cup.
To fix the leaves, a batch of wilted leaves are either subjected to steam or dry heat. Orthodox ways of fixing tea include tossing a batch into a wok heated with wood fire or coal. Conventional techniques include ‘baking’ and ‘pan firing’ as well, carried out in large industrial-sized contraptions. Steamed leaves tend to taste softer than the pan-fired or wok-fired ones which end up taking on some of the toasty notes.
Oxidation refers to the process of browning of the leaves. By allowing the wilted leaves to oxidize/ferment to a desired level of ‘brown,’ enzymatic breakdown of the compounds takes place which produces intense flavours, aromatic compounds, and caffeine, among others.
Right from the moment the leaves are disembowelled from the plant, the cell walls of a leaf start breaking down. Volatile compounds begin to oxidise, and newer, complex compounds begin to develop. If the leaves are allowed to brown to their maximum potential, as is the case when making black tea, polyphenols completely break down into theaflavins and thearubigins. These compounds are responsible for the briskness and the colour that typically define good black teas.
Oxidation is typically carried out in a climate-controlled room where the temperature is maintained at 25-30°C and humidity at 60-70%. Wilted and partially rolled leaves are spread evenly across the floor or placed in trays and then stacked on shelves. These leaves are left to oxidize until a desired level of brown is achieved – complete oxidation lasts as much as 72 hours at times! To halt or slow down oxidation, partially oxidized leaves are moved to a panning trough where they are heated and dried.
Teas that are minimally oxidized tend to retain a lot of their green colour and vegetal flavours since polyphenols do not break down as much. A semi-oxidized tea, on the other hand, has a brown appearance but produces a slightly mellower-looking brew. When oxidized fully, leaves turn brownish-black, and the flavours emerge brisk and intense. An Assam black is a stellar example of a fully oxidized tea.
Rolling refers to the shaping of the leaves into tight forms. Leaves are rolled at multiple stages of the tea’s production, but typically right after wilting, fixing, and oxidation. During the process, essential oils tend to ooze out of the leaves that intensify the aromatic attributes furthermore. Also, the tighter the roll, the longer the shelf life of the tea.
To roll the leaves, a batch is laid on to the rolling plates and slowly rolled by a pressure contraption. Some producers of orthodox tea choose to roll the leaves by hand, although the process takes quite long.
Leaves tend to be rolled into long wiry forms, the most popular style, or into semi-rolled pellets or tightly rolled ones – a common style in Chinese oolongs.
To keep the tea free of moisture, they are dried at various stages of production. Drying helps encapsulate the tea’s flavours and ensure better shelf-life. When drying the leaves, the idea is to bring down the moisture to as low as 1% of the tea’s weight or lower in some cases.
Typically, leaves are dried in an industrial sized oven. The process is carried out gradually to prevent roasting the leaves and turning them unpalatable.
A practice common in the Orient, some teas are subjected to aging/ extended fermentation. Pu-erh, for example, is an aged tea, fermented for years at a stretch. The idea is to draw out more intense and complex flavours, should the leaves have the potential for it.