With the exception of herbal teas, pretty much all the tea that you drink—from the iced green tea chilling in your fridge to the spicy masala chai you order from the local café—is derived from the leaves of the same plant: Camellia sinensis. Once leaves are harvested from the tea plant, the processing operation must begin. How a batch of leaves is processed can lead to vast differences in flavor profile, color, and even quality of the final product.
Understanding how different teas are processed can provide us with a better appreciation of the wide variety of teas on the market. Here, we’ll break down some of the basic terms used in tea processing to give you an idea of what differentiates that earthy oolong from a cup of light and vibrant green tea.
The first step in getting tea leaves ready for market is, well, actually harvesting them. For higher quality teas, the leaves are typically plucked by hand, with workers meticulously snapping off tea buds to collect the leaves.
Hand plucking can be quite painstaking, so machine plucking increases the efficiency of the whole operation—however, harvesting tea by hand is the best way to ensure that the final product is a high quality, artisanal cup of tea. Additionally, there are numerous cultivars of the Camellia sinensis plant that are ideal for specific teas. Camellia sinensis sinensis is often used for green teas, while Camellia sinensis assamica is considered more optimal for black tea production.
When the leaves are harvested can also impact the overall flavor of the final tea leaves. You may have seen different teas labeled “first flush” or “second flush”—these terms refer to the time period in which the leaves were harvested during the harvest season (typically spring through summer). Darjeeling teas are very commonly sold with these labels—a first flush Darjeeling is harvested around March and will typically have a more delicate, milder flavor than its second flush counterpart, which is harvested through June.
Once the tea buds and leaves have been plucked, they naturally wilt and lose some of their moisture. Tea makers typically employ a systematic and controlled wilting process, known as withering. While it’s not the only thing differentiating a green tea from a black tea or an oolong, the withering phase is one of the first steps in tea processing where these varieties diverge from each other.
Essentially, when raw tea leaves and buds are transported to their processing plants, they are laid out in a withering trough or mat and allowed to wilt even further under controlled temperatures and humidity levels (these can vary depending on the type of tea being made and the climate of the region in which the tea is produced). The withering process is particularly useful in that it lowers the water content of the tea by up to 50 percent, which makes later steps in the process, like disruption and fixation, easier.
The duration of the withering process varies from tea to tea. For white tea, a withering period of around three days allows the enzymes in the leaves to develop just the right amount of sugars and tannins (this is why white tea often has a somewhat sweet, almost fruity flavor profile), while black teas typically only undergo a withering process of 14 to 18 hours.
After the initial withering process, black and oolong teas will undergo “disruption.” This usually consists of bruising the leaves and damaging the cell structure a bit, which will encourage even further enzyme activity during the oxidation phase.
If you’ve ever noticed the interior of an apple begin to turn slightly brown after you bite into it, then you’ve witnessed the oxidation process. Oxidation is the process by which exposure to the oxygen in the air triggers a series of chemical reactions within the tea. This actually begins during the withering process as enzymes begin breaking down proteins and other compounds within the leaves.
Processors manipulate the extent to which the leaves undergo oxidation, which is ultimately one of the main determining factors in what kind of tea you’ll end up with in the final product. After leaves are disrupted, oxidation occurs faster than it does during the withering process, and leaves are aired out for up to three hours.
Oxidation and withering are quite similar—for the most part, the same chemical reactions occur during both. Withering can be thought of as preparation for oxidation, as it sort of jumpstarts the later oxidation phase. By the end of the withering process, the tea leaves should still have a mostly greenish color; during oxidation, the tea develops its dark brown color.
As a general rule of thumb, green teas have little to no oxidation (outside of what occurs during a brief withering period), while black teas are fully oxidized. This process not only determines the color of the final product, but it’s also a necessary step in developing the flavor of black teas and oolongs, as a variety of tannins, volatile compounds, sugars and caffeine are all developed during the oxidation phase.
Once the tea has undergone just the right amount of oxidation, tea processors begin what’s called fixation: heat is applied to the tea leaves, denaturing the enzymes in the leaves and inhibiting oxidation from going any further. This process occurs, in one way or another, with all teas except for black varieties, as black tea is fully oxidized.
With green tea, fixation occurs relatively early on, as there should be very minimal enzyme activity. Green tea fixation often involves one of two methods: either steaming them for a very brief period (usually less than one minute) or roasting them in a pan or rotating drum. Similarly, once an oolong variety has reached the ideal oxidation level (lighter oolongs will have oxidation levels closer to that of a green tea, while dark oolongs can go as far as 70 percent oxidation), it will be baked at high temperatures to ensure that it doesn’t oxidize any further.
Once oxidation ends, the tea must be dried of any remaining moisture content. Tea can be dried in a number of different ways, from lying out under the sun to let the water slowly evaporate or by using charcoal roasters.
Now, of course this isn’t an exhaustive tally of all the steps that go into processing your tea. After all, there are so many different types of teas and ways to process them, that it would be impossible to cover everything in one short blog post! Ultimately, it’s a starting point in understanding the meticulous and painstaking amount of labor that goes into producing the expansive variety of teas that we know and love.
About The Author: Practically raised in his family’s kitchen, Andrew Warner's love of food and cooking goes all the way back to his early childhood in Sacramento, California. When he headed off to Los Angeles for college, he began writing about his experiences crafting simple, cheap meals using a three-cup rice cooker, for his award-winning column Dorm Dining at UCLA’s school newspaper, the Daily Bruin. Since then, he’s fallen in love with reporting and blogging about food, serving as a managing editor for the fashionfruit blog. You can usually find him catching up on work at one of his favorite local coffee shops – Temple Coffee in Sacramento or Espresso Profeta in Los Angeles.