Oxidation
Definition
The chemical process where enzymes in fresh tea leaves react with oxygen, darkening the leaf and transforming its flavor profile. Oxidation is the primary factor that distinguishes tea types - green tea is unoxidized, oolong is partially oxidized, and black tea is fully oxidized.
Why it matters
Understanding oxidation helps you predict a tea's flavor character before you even steep it. Lightly oxidized teas tend toward fresh, grassy, or floral notes, while heavily oxidized teas develop malty, fruity, or chocolatey flavors. It's the single most important variable in tea processing.