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

Where the (E(1cm)0.02 %) value for theaflavin gallate dihydrate being 0.747 at 460 nm.
The factors for converting absorbance to percentage thearubigins f2 from the value
obtained at 380 nm is
f2 at 380nm = 0.02 X 375
0.733 X 9
= 1.19
Where the average E 0.02% value for SI and SII thearubigin fractions is 0.733.
The EB values have also been used, with the EA values, for obtaining data on the colour
and brightness of tea infusions. The sum of the absorbancies of solutions A and B can be
used to measure the colour and brighteness of tea infusions. Thus, the sum of the optical
densities of the A and B solutions can be used to measure the colour of the infusion and
the value is the total colour.
iii). Total colour =6.25 X (EA+2EB)
This is virtually the same as the absorbance of the original tea infusion.
Brightness is due to theaflavins, and a measure of ‘brightness’ is obtained by expressing
the extinction value at 460 nm due to theaflavins as a percentage of the total extinction.
Thus, iv) % Brightness= (100 X EB)/(EA+2EB)
Optical density was measured at two wavelengths (380nm and 460nm) because
theaflavins absorb at 380nm and thearubigens absorb at 460nm.
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