---
title: 'Tea leaf chemistry'
url: 'https://howtotea.me/science/chemistry'
markdown: 'https://howtotea.me/science/chemistry.md'
lang: en
date: '2026-11-03'
description: 'Caffeine, catechins, theanine and aroma compounds in tea leaf: how much dry tea holds, what reaches the cup, and which tea risks have been measured.'
---

# Tea leaf chemistry

The taste, smell and lift of a cup come from a handful of compound groups in the leaf. Their shares in dry tea have been measured, and they explain where much brewing advice comes from.

 ![Dry black tea with golden tips and a cup of red-amber tea](https://howtotea.me/images/c/o/v/e/r/cover-9c75130a.webp) Illustration 

By dry weight, the largest group in tea leaf is [polyphenols](https://howtotea.me/science/chemistry/polyphenols), at 18–36%, and catechins make up 70–80% of them. They account for astringency, liquor color and the haze in cooled tea. [Caffeine](https://howtotea.me/science/chemistry/caffeine) runs at 2–5%, highest in the bud and first leaf, and only part of it reaches the cup: a 30-second rinse removes about 9%. The Japanese chemist Sakato Yajiro described [theanine](https://howtotea.me/science/chemistry/theanine) in 1949. Shaded gyokuro and [matcha](https://howtotea.me/brewing/methods/matcha) have the most, [pu-erh](https://howtotea.me/teas/dark/puer) almost none.

Aroma is harder to pin down. Researchers have found about 600 volatile compounds in tea, yet the recognizable [aroma](https://howtotea.me/science/chemistry/aroma) of a given tea rests on a few dozen, and almost all of them form during withering, roasting and other processing rather than in the fresh leaf.

Where [tea safety](https://howtotea.me/science/chemistry/tea-safety) is concerned, the measured risks come less from the leaf than from drinking habits. Temperature comes first: IARC classes drinks above 65 °C as Group 2A. Next comes fluoride, for people who drink liters of brick tea made from mature leaf, and then pesticides. Depending on solubility, anywhere from 1–4% to 90–100% of the residue passes into the liquor.

In this section

- [![](https://howtotea.me/images/c/o/v/e/r/cover-f3d74ee1.webp) Caffeine 咖啡碱 How much caffeine tea leaf holds and how much reaches the cup: the role of cultivar and plucking, heat and time, and why a rinse removes so little. ](https://howtotea.me/science/chemistry/caffeine)
- [![](https://howtotea.me/images/c/o/v/e/r/cover-138b223e.webp) Polyphenols 茶多酚 What tea polyphenols are: catechins in green leaf, theaflavins in black tea, where astringency comes from, why tea clouds, and what to change when brewing. ](https://howtotea.me/science/chemistry/polyphenols)
- [![](https://howtotea.me/images/c/o/v/e/r/cover-b69944f4.webp) Theanine and umami 茶氨酸 What theanine is and where tea umami comes from: shaded gyokuro, amino acids by type, why 50-60 °C water makes a soft cup, and what not to expect. ](https://howtotea.me/science/chemistry/theanine)
- [![](https://howtotea.me/images/c/o/v/e/r/cover-08adbe31.webp) Aroma 香气 Where tea aroma comes from: glycosides, indole, pyrazines, how withering and roasting build them, and how to smell the lid, the steam and an empty cup. ](https://howtotea.me/science/chemistry/aroma)
- [![](https://howtotea.me/images/c/o/v/e/r/cover-88cd27a2.webp) Tea safety 茶汤安全 What in tea is up to you: drinking temperature, fluoride in brick tea, pesticides and rinsing, iron, plastic tea bags. Numbers from studies and standards. ](https://howtotea.me/science/chemistry/tea-safety)

---

## Navigation

- Parent: [Tea science](https://howtotea.me/science.md)
- Next: [Water and extraction](https://howtotea.me/science/water-and-extraction.md)
- Children:
  - [Caffeine in tea and in the cup](https://howtotea.me/science/chemistry/caffeine.md)
  - [Polyphenols: catechins, theaflavins, astringency](https://howtotea.me/science/chemistry/polyphenols.md)
  - [Theanine, amino acids and umami](https://howtotea.me/science/chemistry/theanine.md)
  - [The chemistry of tea aroma](https://howtotea.me/science/chemistry/aroma.md)
  - [Is tea safe? What is in the cup](https://howtotea.me/science/chemistry/tea-safety.md)