Before I began my obsessive and fanatical relationship with tea (my girlfriend's opinion), I was under the impression that green and black tea were the products of entirely different plants. To my edification, I soon discovered that all tea, strictly speaking, is from the same plant. The orthodox definition of tea states that tea is a shrub called camellia sinensis which is part of the Theaceae family. I can imagine the snobby “tea-heads” whom I have met in the online tea community shuddering with disgust at the thought of calling any herb or plant other than camellia sinensis tea. In a more colloquial usage, however, tea refers to a expansive variety of different herbs and leaves. For the sake of clarity though, I too shall succumb to the narrow definition of tea as the product of camellia sinensis. (A note to snobs around the world: language evolves and is flexible.) Herbal “tea”, for those who care to draw the distinction, can be referred to as a tisane (ti-'zan, -'zän).
Alright, so now you are dying to know what creates the drastic variations among tea varieties such as white, yellow, green, oolong, black and pu-erh. In an attempt to make this introduction concise, I will only discuss two of the most influential factors which contribute to the differences among tea varieties.
First, and in my opinion most importantly, the differences among the broad aforementioned categories of tea (white, yellow, etc) are the result of differences in the post-harvest processing of the leaves. The factor most greatly effecting the classification, taste, aroma and appearance of a given tea is the level of oxidation the tea undergoes. Camellia sinensis contains an enzyme called polyphenol oxidase which begins to oxidize soon after the tea leaves are harvested. Oxidation leads to the darkening of the tea leaf and an increase in tannins within the leaf. (Interestingly enough, this same enzyme turns cut avocado brown). The tea farmer can halt oxidation by applying heat to the harvested tea leaves. Some teas undergo 100% oxidation before they are roasted while others are baked before the oxidation process even begins.
White tea, for example, is produced from wilted and unoxidized tea buds and young tea leaves. Simply put, in order to be considered white tea, the tea must contain tea young buds or leaves, and must be unoxidized. Due to the minimal processing of white tea, some have argued that it provides even greater health benefits than green tea.
Yellow tea, like white tea, is unoxidized. Unlike white tea however, yellow tea is unwilted and allowed to yellow before being baked. Green tea is very similar to yellow tea in that it is unoxidized and unwilted, but green tea undergoes a shorter drying period than yellow tea, and thus never turns yellow.
The type of tea known as oolong is arguably the most varied in terms of flavor, aroma and appearance. The diversity within the oolong tea category is explained by the fact that oolongs can undergo anywhere from 10% to 70% oxidation. For example, some oolongs which are oxidized around the 10% range share many characteristics with green tea, whereas oolongs which are 70% oxidized are more comparable to black tea.
If you haven't guessed by now, black tea is the most heavily oxidized of the tea varieties. Black tea undergoes 100% oxidation. As I mentioned earlier, oxidation results in the darkening of the leaf and the production of tannins with in the leaf. Consequently, 100% oxidation results in the blackening of the tea leaf. Based on the appearance of the dried leaves, Westerners have come to know this blackened variety of tea as black tea (genius!). In the East, however, the Westerner's black tea is known as hong cha (紅茶), or red tea, because the brewed liquor is red.
Now on to the good stuff, the Debussy of my tea world - fermented tea. Fermented tea is seldom known outside of the Asian or die hard tea fanatic community. The most widely known hei cha (黑茶), or black tea (the appellation the Chinese have given to fermented teas) is known as pu-erh. Confused yet? While most teas are stored in air-tight containers after production, pu-erh is exposed to the air for years, decades and sometimes centuries. While exposed, pu-erh ferments and oxides. Fermentation and “post-oxidation” mellows the flavor(s) of a tea, giving rise to a smooth and often earthy beverage which is conspicuously different from its unfermented past self.
Post-harvest processing is not the only factor which alters the taste, aroma and appearance of tea. Differences in growing conditions can also result in profound variation among and within these broad categories of tea. Growing conditions are in part determined by the soil structure or climate of a region. For example, Wuyi cliff oolong teas are grown in rocky soils, compelling many to argue that the heavy mineral taste characteristic of many Wuyi oolongs is a consequence of these special growing conditions. Similarly, many attribute the fruity sweetness of Taiwanese oolongs to the fact that many Taiwanese tea gardens flourish in the soil of retired fruit tree farms. Farmers will sometimes more actively alter growing conditions in order enhance or diminish particular aspects of a tea. For example, a much sought after Japanese green tea known as Gyokuro is grown in the shade for 20 days prior to harvest in order to increase amino acid levels while decreasing catechin levels in the plant. Shaded teas are generally sweeter and less astringent than there non-shaded counterparts.
I hope that was interesting. If not, then you must not like tea, because my writing is riveting! (If my arrogance disgusts you, then it was just a joke). When I told a friend of mine that I was starting a blog about tea, his puzzled smile foreshadowed the question I hear again and again. “Is there really that much there, to have an entire blog about tea?” This article is only the top of the tea plant, metaphorically speaking of course. I hope that you will check back to find more tea related articles (by which I mean I hope I write them). Please post comments, corrections or questions if you have them.