Next steps are withering and oxidation

The tea leaves will begin to wilt soon after picking, with a gradual onset of enzymatic oxidation. Withering is used to remove excess water from the leaves and allows a very slight amount of oxidation. The leaves can be either put under the sun or left in a cool breezy room to pull moisture out from the leaves. In a withering room, leaves are spread out along troughs for 8-14 hours, usually overnight. During this time 35 per cent of moisture is lost. The appropriate conditions for withering, such as temperature and relative humidity, are not readily defined in literature as it can vary depending on climate, producing region and type of process used. However, variations in the rate of withering, such as a hard or soft wither, has been shown to influence flavor compounds. The leaves sometimes lose more than a quarter of their weight in water during withering. The process is also important in promoting the breakdown of leaf proteins into free amino acids and increases the availability of freed caffeine, both of which change the taste of the tea.

Known in the Western tea industry as disruption or leaf maceration, the teas are bruised or torn in order to promote and quicken oxidation. The leaves may be lightly bruised on their edges by shaking and tossing in a bamboo tray or tumbling in baskets. More extensive leaf disruption can be done by kneading, rolling, tearing, and crushing, usually by machinery. The bruising breaks down the structures inside and outside of the leaf cells and allows from the co-mingling of oxidative enzymes with various substrates, which allows for the beginning of oxidation. This also releases some of the leaf juices, which may aid in oxidation and change the taste profile of the tea.

For teas that require oxidation, the leaves are left on their own in a climate-controlled room where they turn progressively darker. This is accompanied by agitation in some cases. In this process the chlorophyll in the leaves is enzymatically broken down, and its tannins are released or transformed. The tea producer may choose when the oxidation should be stopped, which depends on the desired qualities in the final tea as well as the weather conditions (heat and humidity). For light oolong teas this may be anywhere from 5–40% oxidation, in darker oolong teas 60–70%, and in black teas 100% oxidation. Oxidation is highly important in the formation of many taste and aroma compounds, which give tea its liquor colour, strength, and briskness. Depending on the type of tea desired, under or over-oxidation can result in grassy flavours, or overly thick winey flavours. This process is sometimes referred to erroneously as fermentation in the tea industry.

Next, the leaves are rolled and dried

Kill-green or shāqīng (殺青) is done to stop the tea leaf oxidation at a desired level. This process is accomplished by moderately heating tea leaves, thus deactivating their oxidative enzymes and removing unwanted scents in the leaves, without damaging the flavour of the tea. Traditionally, the tea leaves are panned in a wok or steamed, but with advancements in technology, kill-green is sometimes done by baking or panning in a rolling drum. In some white teas and some black teas such as CTC blacks, kill-green is done simultaneously with drying.

The damp tea leaves are then rolled to be formed into wrinkled strips, by hand or using a rolling machine which causes the tea to wrap around itself. The most commonly used rolling machines are big, circular rotators that press the leaves between two grooved wooden plates which tear, squeeze and bruise the leaves. The roller machines can process up to 25kg at a time. This rolling action also causes some of the sap, essential oils, and juices inside the leaves to ooze out, which further enhances the taste of the tea. The strips of tea can then be formed into other shapes, such as being rolled into spirals, kneaded and rolled into pellets, or tied into balls, cones and other elaborate shapes. In many types of oolong, the rolled strips of tea leaf are then rolled into spheres or half spheres and this is typically done by placing the damp leaves in large cloth bags, which are then kneaded by hand or machine in a specific manner. The tea can also be pressed into bricks through the use of heavy stones or presses.

Drying is done to finish the tea for sale. This can be done in a myriad of ways including panning, sunning, air drying, or baking. Baking is usually the most common. Great care must be taken to not over-cook the leaves. The drying of the produced tea is responsible for many new flavour compounds particularly important in green teas.

While not always required, some teas require additional aging, fermentation, or baking to reach their drinking potential. For instance, a green tea puerh, prior to curing into a post-fermented tea, is often bitter and harsh in taste, but becomes sweet and mellow through fermentation by age or dampness. Additionally, oolong can benefit from aging if fired over charcoal. Flavoured teas are manufactured in this stage by spraying the tea with aromas and flavours or by storing them with their flavorants.

Finally, the tea is sorted, packaged and shipped.

Tea sorting can help remove physical impurities, such as stems and seeds. Using sorting equipment to improve tea production efficiency is very common in tea processing plants, especially in black tea processing. A Color sorter may also be used to classify final product grades according to color and shape.

After that, the tea is packaged and shipped to distributors, retail stores, coffee and tea shops, and directly to customers. Then you can buy a tin of loose leaf tea, a box of bagged tea, or cup of tea to enjoy.