Chemistry and Tea

If I can just be obvious for a moment, I absolutely love tea. I'm not super picky about the kind of tea that I drink, but.. actually nevermind. I'm very picky. I'll drink whatever is around but if I'm the one picking out the concoction, odds are it's going to be some perfected blend of whatever strikes my fancy at that moment. I'll amp up the caffeine as much as possible and do my best to pack as much flavor as I can into one single steamy-hot cuppa. 

Currently, I'm on a peach oolong kick. 

There are a lot of teas out there. Oolong, bullet, black, green and even white tea. There are even herbal teas that have been used therapeutically and even medicinally for thousands of years with touted effects backed by peer-reviewed experimentation and testing. In fact, white willow bark, made into a tea, can alleviate pain and inflammation because one of its constituent ingredients - a chemical flavonoid called salicin - is chemically similar to an everyday NSAID pin reliever - Aspirin! 

Aside from herbal teas, though, you might be surprised to know that most of what we would call tea is actually derived from a single plant called, uniquely, the Tea Plant - Canellia sinensis. More surprisingly, it's actually a kind of evergreen shrubbery! 

 

It's true. We really do.

So how does a single plant make so many different kinds of tea? Why do they all look, taste and even feel so different in your mouth (and skin, if you're anything like me)? 

One word: Oxidation. 

What is Oxidation 

Oxidation is a chemical reaction; the same biochemical process that causes bananas to turn brown is the same process that gives each form of tea its distinct flavor profile and color. It turns metal into rust. It's also the same process that causes certain fruits to "go bad." Interestingly enough, when you see leaves turn brown in the fall and drop off the trees, you're witnessing oxidation.

Oxide is air. So, basically, it just means that something is being exposed to air. 

Polyphenols
Oxidation in tea is all about polyphenols - more specifically the enzymes polyphenol oxidase and and peroxidase (per = each, oxide = oxygen; One -ase for each oxide. Congratulations, you now understand chemical names!). 

In order for oxidation to occur, the contents of a cell must be exposed to air. This means that they must be damaged. This can occur when a cell dries out, but also via other mechanical means such as rolling them in bamboo or just plain beating the crap out of the leaves. When those contents are exposed to oxygen, the chemical process of oxidation begins. This takes the polyphenols like catechins  and turns them into the delicious chemicals we know in the taste of tea. Chemicals like theaflavins and other flavinoids. 

Purple tea contains a lot of antioxidant polyphenols called anthocyanins and is from a special cultivar of our beloved tea plant called var. Assamica grown in Africa. And yes, it exists. 

These chemicals don't just provide taste, but they also supply the color. Theaflavins, for example, not only add that bright, almost tart taste to a good green tea, but it also gives the tea its yellow color. Theaburgins give tea a red color and a deep, earthy flavor. And when you're getting a green tea, you're seeing chlorophyll.

Many Teas, One Leaf

So, now you know the process that gives tea its flavor, color and other characteristics, and you know that it all comes from one plant. But how do you get so many varieties from one leaf? 

Each type of tea has a different method by which the contents of the cells are exposed, time the leaves are harvested, as well as how much oxidation is allowed to occur before it is halted. That's it. Subtle details in harvest and processing creates all of these wonderful flavors and types of tea. 

Black Tea is fully oxidized. Oolong is only partially oxidized. And Green Tea experiences almost no oxidation which leaves more chlorophyll and gives the tea its characteristic green tint and hue. White Tea, one of my personal favorites (when I can find the stuff), is virtually untouched and unprocessed, which allows virtually no oxidation to occur. 

Fermentation

Oxidation should never be confused with fermentation. Oxidation is when a thing is exposed to oxygen. Fermentation is a biological process in which yeasts and bacteria process something into something else. Saurkraut, beer and other great foods are made in this way. It is also used to make a few types of tea as well, such as kombucha and Pu'erh tea (another personal favorite).

Just remember, no matter what kind of tea you're drinking..