Glossary
Oxidation
The natural chemical browning of picked tea leaves when exposed to air, which shifts flavor from green toward black.
Oxidation is the chemical reaction that occurs when tea leaves are bruised or rolled after picking and their internal compounds are exposed to oxygen in the air, similar in principle to how a cut apple browns. In tea production, makers control how much oxidation happens before applying heat to stop the process.
The amount of oxidation is what separates the major tea styles from a single plant: minimal oxidation gives green tea, partial and variable oxidation gives oolong, and full oxidation gives black tea. Understanding this one variable explains why teas from the exact same bush can taste completely different depending on how they were processed.
For buyers, a package that mentions oxidation level or processing style is giving a genuine clue to expected flavor before you brew a single cup. A common mistake is confusing oxidation with fermentation, which is a separate, ongoing microbial process seen mainly in aged pu-erh rather than in green, oolong or black tea.
Where this comes up
- Green vs Black vs OolongArticle
- Best Loose Leaf Black Tea for Bold Daily CupsBuying guide