What is tea? That sounds like a simple enough question. Why, it’s a beverage, of course! Made from, like, leaves and stuff! Sure, okay. But specifically, when we talk about tea we’re referring to the infusion of a certain perennial evergreen plant called Camellia Sinensis. This includes all of varieties of Camellia Sinensis that are found around the tea-growing world, but does not include a whole host of things we commonly refer to as tea. So then, what’s not tea? Herbal infusions, technically speaking, are not tea; not rooibos, nor chamomile, nor mint, and so on. These “teas” are actually “tisanes,” as they are not derived from the species of Camellia Sinensis.
There’s a wonderful world of tea out there to explore, but one of the basic challenges to new tea drinkers is understanding how one tea type differs from another – say, green vs black. The reality is, tea is so heavily dependent on how it’s processed after harvest that any tea leaf can be turned into a black, oolong, green and so on. There’s literally no one out there growing black tea, for instance. So as a sort of Tea 101, I thought we’d spend a little time discussing, in general terms, how the major tea types are created.
Steps in Tea Production
In one way or another, all tea is processed using the same few steps – withering, oxidation and drying. We’ll focus mostly on the oxidation step, since it has such a dramatic influence on the resulting flavor and aroma of the tea. But here’s a brief description of each.
Leaves that are removed from a plant begin to wilt and lose water. This is known as withering, and it’s the loss of moisture content that allows the leaves to become malleable and ready for further processing. During this step, flavors and aromas start to concentrate in the leaves.
Then, some level of oxidation is initiated and then stopped at a specific point. Oxidation is what happens when the cellular structure of a plant breaks down and is exposed to oxygen. The result of oxidation is the browning of leaves and changes in the aroma and flavor. Some teas can be very lightly oxidized, heavily oxidized or anywhere in between. This oxidation step has a serious impact on the resulting tea, so it’s where we’ll be spending the bulk of our attention.
The last step we’ll cover here is drying, which is a step that ensures the moisture content of the leaves is reduced enough so that the tea is shelf stable.
Style: Green Tea
Green teas are prized for their freshness and vegetal qualities, so the goal with tea leaves that are destined to become green tea is to halt the oxidation process immediately so they do not brown and change flavor. This is generally done by pan-firing the leaves or steaming them briefly, before raising the temperature to a level in which the enzymes in tea become denatured (halting oxidation). Because freshness is prized in green tea, and the relative low oxidation of the leaves (compared to other styles), it is best to drink green teas soon after they have been harvested and processed.
Style: White Tea
White tea is made by withering the leaves for several days and then drying them (or just withering the leaves until they are dry). This extended withering time allows the leaves the slightly oxidize and the aroma and flavors to develop, providing white tea with a more intense floral aroma than most green teas. The long withering process halts enzyme activity, so no further oxidation will occur.
Style: Oolong Tea
Oolong tea is fascinating because it occupies a broad range of oxidation – from teas that are nearly green tea levels to those bordering on black tea territory. Lightly oxidized oolongs have a vegetal quality, high floral fragrance and buttery mouthfeel. At medium levels of oxidation, intense fruit tones of arise. Finally, with heavy oxidation, oolongs express more dark fruit notes, and sweet and savory qualities like chocolate and nuttiness. Oolongs are oxidized by a characteristic bruising step, in which the leaves are shaken or tumbled so that cellular damage occurs. The leaves are then heated to the point in which the oxidation is halted, locking them into place along the spectrum of oxidation.
Style: Black Tea
On the higher end of oxidation we have black teas. Black teas undergo an oxidation step that breaks down the cellular walls of the leaves by rolling. Rolling is typically done on special rolling tables, which apply pressure to the tea and expose its broken cellular walls to warm, oxygen-rich air that passes over the tea bed. Depending on processing, black teas can be sweet, malty, fruity or savory.
There are certainly other styles of tea out there (including ones we feature on our menu at Mammoth Espresso), but understanding the role oxidation plays in tea processing is a fantastic starting point in your tea journey. I welcome any questions about tea via e-mail at info@mammothespresso.com or during one of our weekly tea tastings, which happen every Wednesday at 2 pm.