Updated 20 April 2019.
The chemistry of tea can be quite a mystery but also very important to your enjoyment of this fine beverage. Awhile ago, we posted about tea and caffeine (one of the chemicals occurring naturally in tea – see article here). But there are more things to consider, especially if you are trying to assess the benefits of tea to your health. This little teapot set out to find out more, sort through it, and present some clear facts to you. I failed, dear tea loving humans, mainly due to how convoluted, obscured, and contradictory a lot of that info is. Plus my desire never to lead you astray. TOOOT!
On a side note, let me say that everything is chemicals, so whenever you see someone dissing something as “chemical” and praising another as “natural,” please let them know. (Just the wordsmith in me speaking up here – TOOOT!)
Quite a few humans have devoted a lot of time to studying the chemistry of tea, some doing a better job of it than others, reputations notwithstanding (some humans are better at promoting themselves). While looking into the information on this topic available online, we came across a number of articles by non-scientists and by someone who is a scientist but seems to present ideas that are a bit, well, off-topic and not very well founded in true objective science. And when he says that tea is, next to water, the most natural beverage on earth, we can only think that that does not make it good for you (a lot of “natural” things are dangerous and even deadly). We also found some actual studies that have been done in labs by scientists seemingly bent on producing the kind of results that keep them getting grants. The papers they write about the results are a bit complicated and, frankly, a rather dry way of presenting such important information, and several seem to contradict each other. *sigh* TOOOT!
A Useful Bit
We did come across various numbers on how much of certain chemicals are in tea. However, the amount of each chemical in a particular tea seems to vary widely. It depends on a number of factors, including the testing methodology used. We combined them into one table showing the range of numbers. It will give you a fair idea of what is in that teacup and how inexact the science of tea seems to be after hundreds of years of enjoyment and study.
Areas Affecting the Chemistry in Tea
From leaf to cup can be quite a journey. And each step affects the chemistry in tea. This is clear. What remains muddled is how much each effect is. In fact, finding any reliable figures was a hopeless quest. Some were hidden behind a pay wall. Others canceled each other out by saying totally opposite things. Even the definition of something as common as “tannins” was presented in contradictory ways. But these areas definitely can make a big difference in flavor, and that in itself shows the difference in chemistry of the various tea types.
The Raw Leaves
The tea leaves have certain chemicals in them at time of harvest. What they are and in what quantities are affected by:
- There are also HUNDREDS or even THOUSANDS of tea plant cultivars! Some are grown to make specific styles of teas such as Dancong oolongs or particular Taiwanese oolongs and many are developed to resist various plant diseases and pests; plant age is also a factor.
- Terroir includes slope (hilly or flat), elevation, rainfall amounts, mists/cloud cover, soil quality, drainage, and temperatures.
- Cultivation is key. Tea growers have been pushed to using organic methods for fertilization and pest control, but otherwise, cultivation has improved over the years. Methods include pruning and other plant care, such as shading plants during a certain part of their growth before harvest or letting the plants grow wild.
- Harvesting is a big factor in tea flavor. In fact, Qing Ming teas (those harvested before the Spring rains in China) are considered premier teas! The time of day (some are harvested while the morning is still cool but the dew is gone) is also a factor.
- From where on the plant the leaves are plucked (many are made of top leaf buds plus 1-2 tender leaves growing just below them, but others are made of leaves growing below those, and still others are made of just the stems left after leaves are processed for other tea styles).
- Tea leaves need to be handled carefully after harvest to avoid bruising that can cause premature oxidation; especially important for leaves destined to be made into white, yellow, and green teas.
The Processing of the Leaves
Harvested leaves go through various processes, according to the style of tea being made.
- Withering: Done for all teas except white teas.
- Rolling: Done for oolong, black, and pu-erh teas. Is often repeated for hand-processed teas.
- Oxidizing: Done for all teas except white and green teas. (A small amount of oxidation may occur in processing leaves for green tea.)
- Drying: Done for all teas except white teas. Aka firing, frying. Often done repeated for premier teas. Tea processing stopped here except for pu-erhs and aged teas.
- Fermenting: NOT the same as oxidation. Processed leaves undergo a chemical reaction of enzymes and bacteria that further break down the leaves and make them infuse a smoother, usually non-bitter liquid.
- Storing: Important for all teas to protect them from air (that can let in moisture and odors), light, and heat. Especially important for proper aging of pu-erhs.
What chemicals and their amounts will be different for each. However, we could find no sources that agreed with each other on what these were and the amounts.
The Steeping of the Leaves
A wide variation of results can occur here, not just in the chemistry of tea but also in the taste they help create (along with the quality of the water and anything you add to the tea before, during, or after steeping). One thing is for sure: the aroma of the dry tea leaves does NOT necessarily come through in the liquid infused from them.
A Bit About Phenolic Compounds
While tea analysis is full of contradictions, a number of chemicals have been clearly identified and studied. The key ones basically fall under the category of phenolic compounds (polyphenols). They can be as much as 40% of the dry weight of processed tea leaves. They provide astringency (that dry-mouth feeling after taking a sip of tea) as well as color and flavor (from two phenolic substances theaflavins and thearubigins, which are formed from flavanols during tea processing) and, some claim, various healthful antioxidant properties. If you steep up your tea strong, an 8-ounce cupful could have about 240mg of polyphenols.
One thing to note, though, is that among various plant-based foods you humans consume, tea is low on the list of polyphenol content. That means that you have to consume a lot to get the touted health benefits, but that can also cause health problems, especially from the tannins. So, as always, we say to consult your doctor if you want to consume tea for your health and not just for its enjoyment.
Caffeine can also be an issue, despite the counteraction of L-Theanine. Caffeine gives you humans a bit of a boost but can also make you jittery and have a bit of a “crash” after it has worked through your system. L-Theanine helps prevent the jitteriness and the “crash.” It is said to reduce mental and physical stress, improve your brain functions, and boost your mood and mental performance in a conjunction with caffeine. However, some claim that these benefits are negligible or non-existent. While Japan swears by them, the European Union bans such benefit claims from appearing on tea products sold there. A tough line for tea vendors to balance on. And another example of those contradictions out there about tea.
Tea also contains amino acids, enzymes, minerals and vitamins, and more than 700 aroma compounds in trace amounts. But we couldn’t find a comprehensive list of these.
We did find a ranking of tea (black and green styles) among a group of plant-based foods containing phenolic compounds (we added the pictures).
Click on a photo and then scroll through them:
Tea, in moderation, is still a great way to stay hydrated, and that, dear humans, is a very good thing for you. But if you’re looking for tea as a health cure, I advise a trip to your doctor instead. Any article you see saying otherwise is ignoring the hard facts and only interested in promoting the sale of tea. We here, on the other hand, care about you. TOOOT!
There are many humans writing about the chemistry of tea, but sadly most of them are just rehashing things (and often distorting them in favor of making tea look more positive) or spouting the latest nonsense, not facts, about tea or other topics outside of their field of study. Not good for you tea drinkers. And certainly not up to our standards of diligent research and sticking to the facts. So we have a short list of recommended reading. TOOOT!
Try taking a look at these:
- A great PDF with comprehensive information on the chemistry of tea. – sadly, document is no longer available as of 20 April 2019
- Another great PDF of a study of the chemistry of tea. – Sadly, no longer available
- About phenolic compounds in plant-based foods.
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Hi, humans, this site is under my editorial excellence. I, your lovable and sassy Little Yellow Teapot, authors articles on tea, etc., and edit the occasional guest article. All in the interest of helping you humans have a better tea experience. TOOOT!