In black tea manufacturing, one of the most important
steps is fermentation which influences the quality of tea.
The macerated tea leaves were fermented at various temperatures
(20, 25, 30, 35 °C) for different duration. Changes in
polyphenoloxidase and peroxidase activities, depletion patterns
of individual catechins, differences in individual
theaflavin levels and formation of thearubigins were
... [Show full abstract] measured
in leaves during fermentation. Higher stability of
polyphenoloxidase and peroxidase enzymes was observed at
lower temperature (20 °C), and increase in temperature, led to
enzyme instability. The rate of degradation of all the catechins
was found to be fastest at 35 °C and slowest at 20 °C. The
formation and depletion of individual theaflavins varied with
temperature and fermentation duration. The time required for
the formation of maximum total theaflavins (TF) was highest
at lower temperature and this time duration also varied for
different theaflavins formation. Maximum amount of
thearubigins (TR) content and liquor colour development
was observed at 35 °C, and decrease in temperature reduced
thearubigins accumulation. However, maximum brightness as
well as TF/TR ratio was obtained at 20 °C, which suggests
that fermentation at lower temperature is suitable for
manufacturing quality black tea.