Thearubigins
Definition
Large red-brown polymeric pigments formed during the oxidation of catechins and theaflavins in black tea. Thearubigins contribute body, color depth, and much of the soft sweetness of black tea liquor.
Why it matters
Thearubigins are a chemically heterogeneous family of polymerized polyphenol oxidation products formed late in black tea oxidation. They are larger and less well characterized than theaflavins, but they are typically the most abundant phenolic class in black tea liquor. Thearubigins contribute the deeper red-brown core color of black tea, distinct from the brighter orange-red rim contributed by theaflavins. They also add body, softness, and a perceived sweetness, balancing the briskness of theaflavins. In heavily oxidized teas such as Yunnan dianhong or rich Assams, thearubigins dominate the cup chemistry. The ratio of theaflavins to thearubigins is sometimes used as an indicator of black tea quality, with too high a ratio suggesting under-oxidation and too low a ratio suggesting over-oxidation or aged stock.