Chemical Composition of Green Tea

Before we start drinking our green teas, we should first talk about the chemical composition of green tea! There are a few different chemical components in the tea leaf, and they all serve different functions when it comes to the taste and the health properties of the tea plant. We set up this article so that you have a guide to the chemical composition of green tea. Without further ado, let’s get started and explore the many chemical components that make tea the delicious drink that it is.

Green Tea Polyphenols

An important part of the chemical composition of green tea is the polyphenols. Polyphenols are natural compounds in the tea plant that give the drink a lot of its trademark flavor. The term polyphenols includes smaller subgroups of flavanoids, phenolic acids and tannins. The largest subgroup within the polyphenols are the flavanoids. The bitter or astringent flavors you get from a tea are likely from the presence of these flavanoids. It’s believed that flavanoids are the chemicals produced by a plant in order to defend itself against insects, bacteria and fungus. Teas higher in polyphenols are going to be the unshaded sencha teas. You can identify these because they will have less of a sweet flavor, and more of a dry or bitter taste. Black teas will also be significantly lower in polyphenols because during the oxidation process, the plant converts these polyphenols into theaflavins.

Catechins and Antioxidants

One of the more talked about properties of the chemical composition of green tea is EGCG. EGCG (Epigallocatechin gallate) is one of the most important catechins in green tea. It’s thought to have strong antioxidant effects on the body, as it protects it from free radical damage. When researchers study the health effects of green teas, EGCG is one of the chemicals they examine.

Tannins are often misunderstood in the world of tea. The word has historically been used to describe the agents in wood that were used to tan animal skins, however they are in fact a subclass of bitter polyphenols. Although tannins do exist in tea, they are in a very small concentration and therefore do not contribute much to its overall taste. When you are describing the flavor of a tea, use the words catechins or polyphenols instead of tannins.


While the enzymes may not have much to do with the taste of the tea, they have everything to do with the tea's transition into an oolong or a black tea. The two main enzymes in tea are polyphenol oxidase and peroxidase. After the tea leaf is picked, the cells begin to break down and these enzymes are able to convert the polyphenols into theaflavins and thearubigans. This process turns the color of the leaf from green to brown, just like how an apple changes from yellow to brown after it’s bitten and exposed to the air. 

Amino Acids

When it comes to the flavor of a green tea, one of the most important parts of the chemical composition of green tea comes down to the amino acid profile. The most common amino acid in tea by far is L-theanine. This is actually a very rare amino acid in the plant kingdom as a whole. It was discovered in green tea as recently as 1949, and to this date it has only been identified in 3 species of plant and fungus: Camelia sinensis, Ilex guayusa and a species of bolete mushroom native to North America and Europe. L-theanine is thought to be responsible for the reported “calm-alert” feeling that tea is famous for. It is thought to increase alpha brainwave activity, leading to a greater sense of relaxation and a way to decrease mental and physical stress.

Volatile Compounds

Probably the least talked about part of the chemical composition of green tea is the volatile compounds. Although these aren’t talked about much, they are one of the most important parts when it comes to the flavor and aroma of the tea. Primary volatiles are the chemical components emitted by plants when they are attacked or damaged. Secondary volatiles can be brought out of the plant during the production process. In the context of tea, they are responsible for these beautiful floral or nutty notes you may get with the tea. Here are a few that may be worth knowing:

  • Hexanal: fruity and grassy flavors
  • Hexenol: herbaceous and woody flavors
  • Linalool: floral, sweet and woody flavors
  • Geraniol: rosy, floral, geranium flavors
  • Pentanal: almont, malty flavors
  • Benzenacetaldehyde: hyacinth or lilac flavors and aroma


Let’s discuss the thing most tea drinkers seem to be interested in, caffeine. Caffeine is something that exists in all different types of teas. While some teas are significantly higher in caffeine than others, almost all teas naturally contain some level of caffeine. Caffeine levels in tea range from the low caffeine teas like Kukicha to the very high caffeine teas like Gyokuro and matcha green tea powder, which can have as much caffeine as a cup of coffee. 

Why is Caffeine part of the Chemical Composition of Green Tea?

Let’s quickly learn a bit about why tea has caffeine. The tea plant naturally produces caffeine as an insecticide to protect its leaves from insects. The younger, more tender sprouts of the tea plant are more vulnerable so they need to produce more caffeine. The older, more mature leaves at the base of the tea plant are tougher, and less likely to be eaten by insects, so they produce less caffeine. This means that  when the tea is made from older leaves, the chemical composition of green tea will be different. Teas made from older tea leaves will contain less caffeine and teas produced with younger tea leaves will have more caffeine, all else being equal. An example of this is a tea called Bancha. 

Bancha is a tea made from the older leaves of the tea plant, and it contains less caffeine than a normal sencha, which is made from the younger leaves of the tea plant. This tea is nice to enjoy in the late afternoon or evening, especially after a meal. The flavor is a bit softer, with notes of popcorn, cereal and wood. It contains about 40mg of caffeine, less than half the amount of a small cup of coffee.

Another factor that can influence the chemical composition of green tea with regards to caffeine is the ratio of stems to leaves. Because caffeine is only produced in the leaves of the tea plant, teas that include stems like Kukicha and Karigane are going to be lower in caffeine. These teas contain as little as 18mg of caffeine per cup, making them half as caffeinated as a Bancha, and less than a quarter the caffeine of a small cup of coffee. 

The additional stems in Karigane and Kukicha can create a milder tasting experience in the tea. For instance, a pure leaf tea like Gyokuro may have a really intense savory flavor, but the addition of the stems in the case of Karigane can balance it out, creating a nice subtle tea with notes of cucumber and summer grass. This tea is also great when prepared as a cold brew.

Changing the Chemical Composition of Green Tea by Cold Brewing

Cold brewing can be a great way to reduce the caffeine content of a tea. Caffeine is extracted faster at warmer temperatures, so by using cooler water you extract less. You also extract less of the bitter Catechins of the tea, making it smoother and sweeter. If you would like to enjoy a tea as a cold brew without giving up the caffeine, simply brew the tea overnight. The additional time should compensate for the lower temperature water and extract roughly the same amount of caffeine.

Changing the Chemical Composition of Green Tea by adding roasted rice

To reduce the caffeine content of a tea, you can also add some toasted rice to it. Because the rice doesn’t contain caffeine, it brings down the average caffeine content. Teas made with toasted rice are called Genmaicha and they are becoming a common way to enjoy tea without as much of the caffeine. A lot of genmaicha teas are made from older tea leaves as well, which reduces the caffeine content even further. Here you can expect to get around 40mg of caffeine per cup, if you’re using the same 5 grams of leaves.

Changing the Chemical Composition of Green Tea by roasting

Another thing that changes the chemical composition of green tea and reduces the caffeine content is roasting.. During the roasting process, the caffeine in a tea is reduced slightly, making fully roasted teas like Hojicha a good option in the afternoon or evening time. With Hojicha, you may expect to get around 40 milligrams of caffeine per cup, compared to a regular sencha which can have around 60mg of caffeine per cup. If you really want to lower you caffeine intake, you can go for a roasted stem tea, or Kuki Hojicha like this one from Mr. Issin. Not only is it lower in caffeine than a normal hojicha, the stems also roasted differently than leaves, giving the tea a much darker flavor, almost like coffee.

Teas high in caffeine

If you are looking for a high caffeine tea, you will want to go for either a shaded sencha, a Gyokuro or a matcha. These teas are made from younger tea leaves that are shaded for a long period of time and they don’t include many stems. The shading process influences caffeine content more than any other single factor. When the tea plant is cut off from sunlight, it becomes more vulnerable to insects so it needs to produce more caffeine to protect itself. Sencha teas that are shaded for 1 week before the harvest have more caffeine than unshaded senchas and Gyokuro that is shaded for 3 weeks before the harvest has even more caffeine than regular shaded sencha. As a result, Gyokuro contains the highest caffeine content of any Japanese green tea.

A cup of strong Gyokuro can have as much as 120-140mg of caffeine per cup, compared to a cup of coffee that has 80-120mg of caffeine per cup. The reason the caffeine level is so high is because no other leaf tea is shaded for quite as long as Gyokuro. During the shading process, the tea also develops theanine which serves two important functions. First, it produces a smooth, sweet and savory flavor that shaded teas are known for and it also slows the absorption of caffeine. People that drink Gyokuro report having a longer lasting energy throughout the day compared to coffee, without the crash or any jittery energy.

Matcha can be very high in caffeine, but it depends on how it’s made. Low quality matcha can have about half the caffeine as high quality matcha. This is because lower quality matcha skips certain steps of the production process. Either it is made from lower quality leaves, it’s made from unshaded leaves or it doesn’t have its stems removed prior to grinding. All of these factors can lower the caffeine content in a matcha. It also produces a more bitter matcha that isn’t as enjoyable to drink.

As you can see, there are a number of different factors that can greatly influence the chemical composition of green tea. Whether you are looking for a soothing, low caffeine tea for the evening time, or a high energy tea for the morning, chances are you can find it in the world of Japanese green tea. 

Final words on Chemical Composition of Green Tea

I hope you have enjoyed this guide to the chemical composition of green tea. If you have any questions or you have anything you think we might have missed in our guide, please feel free to reach out via email or social media. Until then, we’ll see you next time!

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