As mentioned already, when green leaves are processed, these compounds break down, form complexes and form new compounds. In black tea manufacture, during fermentation a series of biochemical and chemical reactions take place leading to formation of oxidised polyphenolic compounds like thearubigins and theaflavins that are characteristic of tea along with volatile flavour compounds that impart characteristic aroma to tea.
The average chemical composition of black tea (Orthodox and CTC) made from Assam clones is as follows:
|Composition||Orthodox Teas||CTC Teas|
|Water soluble solids %||39.52||41.12|
|Flavour volatiles *d||18.40||8.20|
|Total fibre %||19.35||18.93|
|Chlorophyll a mg/g||1.38||0.48|
|Chlorophyll b mg/g||0.77||0.58|
(*d Sum of total area of GC peaks compared to internal standard compounds)
Biochemical Compounds Responsible for Quality of Tea
Different biochemical compounds are responsible for different quality components of black tea.
|Flavonol glycosides||Light yellow|
|Thearubigin||Ashy and slight astringent|
|Linalool, Linalool oxide||Sweet|
|Nerolidol, Benzaldehyde, Methyl salicylate, Phenyl ethanol||Fruity|
|Trans-2-Hexenal, n-Hexanal, Cis-3-Hexenol, Grassy, b-Ionone||Fresh flavour|