a study of the quality of a local herbal tea and volatiles of parinari ...

3.6.3 Calculations of total theaflavins, total thearubigins, total colour and
brightness
The theaflavin and thearubigin contents were calculated from the following relationships:
i). % theaflavins = 6.25 x Ec x f1
ii). % thearubigins = [(12.5ED + 6.25(EA – EC)] x f2
Where f1 and f2 are the corresponding spectrophotometric conversion factors. The value
of the factor f1 used for calculating the percentage theaflavin (as in equation i) as
anhydrous theaflavin gallate of the sample of tea from the reading obtained at 380nm is
f1 at 380nm = 0.02 X 856.7 X 375
2.225 X 892.7 X 9
= 0.36
Where the (E(1cm) 0.02 % ) value for theaflavin gallate dehydrate of molecular weight
892.7 is 2.225 which is the infusion being prepared from 9 g of tea and 375 ml of water.
The value of f1 used for calculating the percentage of theaflavin (as anhydrous theaflavin
gallate) from the reading obtained at 460 nm is
f1 at 460nm = 0.02 X 856.7 X 375
= 1.07
0.747 X 892.7 X 9
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