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Blog 151: Enzymes and The Taste of Tea

To be fair, tea-making is perfected by time. Tea-making has a history of over thousands of years, and many tea-making techniques were originally discovered or developed by accidents or by ancient tea makers’ countless blind experiments.

This is why many today's tea makers cannot effectively explain the purpose and the reason behind certain tea-making procedures. After all, tea-making is all about hands-on experience, and most tea makers learned tea-making from their elder generation.

Luckily, modern technology allows us to know more about exactly what matters in tea-making and how tastes and aromas are developed and transformed. In today’s blog, let’s talk about enzymes and the taste of tea. (Spoiler alert: this blog can be quite academic.)

Enzymes are extremely important in the overall development and transformation of tea leaves’ ultimate tastes. In fact, water-soluble pigments formed in enzymatic oxidization and non-enzymatic oxidization are crucial flavor elements. TFs (theaflavins), TRs (thearubigins), and TBs (theabrownins) also contribute to the overall tastes of tea.

The color and the taste of tea leaves are affected by characteristics, transformation patterns, and variants of tea polyphenols’ oxidization. Sometimes, tea makers need to balance the development of tea leaves’ colors and tastes.

For example, spreading fresh leaves evenly on ground in green tea tea-making can be detrimental to the color of leaves, but this method is great for developing leaves’ tastes. Therefore, in green tea tea-making, an appropriate level of leaves-spreading can reduce the bitter taste, but too much leaves-spreading can destroy fresh leaves’ charming green color.

When fresh leaves from the same cultivar are made into different tea categories, the level of caffeine doesn’t vary much, but fragrance substances associated with enzymes will have a significant difference.

The level of polyphenol content decreases when the level of fermentation increases (dark tea being the exception. Its polyphenol content is between yellow tea and white tea). Green tea has the highest polyphenol level, and black tea has the lowest. There’s a 1.8x difference between green and black tea. The reason of this different is that teas with low fermentation (such as green tea) have a “kill-green/杀青” procedure that depurates endogenous enzyme.

Besides polyphenols, catechin acid content in tea leaves also decreases with fermentation level increase. Except for few tea categories, teas with the“kill-green/杀青” procedure commonly have more catechin acid content than teas with the “withering” process. Green tea has the highest content, which is 2.43x higher than black tea’s.

These changes indicate that the oxidization of enzyme is crucial to tea polyphenols and catechin acids.

In practice, Wuyi oolong’s “shaking/摇青” technique is a great example of how tea makers control the enzymatic oxidization.

In our Wuyi oolong tea-making, the shaking process must be conducted in a controlled environment called “Qing Jian/青间” (meaning: green room or leaf room). In Qing Jian, temperature and humidity are strictly monitored and maintained.

For centuries, Wuyi oolong tea makers have used “Qing Jian” for the shaking process. But if you ask them why can’t they do this is an open environment, the answer is always “because shaking leaves in a Qing Jian gives us better leaves”.

Finally, in a 2003 study, we revealed why Qing Jian, or a controlled environment, is better for the shaking process.

Essentially, the “shaking” manipulates the enzymatic oxidization, and restricts the oxidization in just parts of a leaf (the edge of a leaf). In a regulated environment, aqueous extracts, tea polyphenols, catechin acids, and amino acids have a slower rate of decrease than those in an open environment. As a result, tea leaves during the shaking process can better retain major flavor substances.

Of course, in our daily tea-making, our tea makers don’t really need to know all the science behind what they do. Actually, knowing the numbers, chemistry terms, and theories won’t help in our tea-making. What our tea makers do have been proven the most effective by history.

Although modern technology can explain lots of scientific theories behind tea-making, there’re still many unknowns that it cannot answer. We hope this blog can help you better understand where most tastes in a good tea come from.

We hope you enjoyed today’s blog. As always, if you have questions or suggestions, please leave a comment, tweet us @valleybrooktea or email the author directly at Please also follow us on Instagram @valleybrooktea and join our mail list to get our daily tea updates and our latest promotions!

This is a Valley Brook Tea original blog. All rights reserved.

1 Comment

Dec 23, 2023

I know they aren't considered big name teas, but if you could do a post on dark tea (puer) and yellow tea, (including the process, flavor profile, and why they aren't as common/cultured) I would definitely read it!

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