The individual sample (1 mL of 25 µg mL−1
tea polyphenols, tea polysaccharides and tea protein), 2 mL of 2.51%
(w/v) linoleic acid in ethanol, 4 mL of 0.05 mol L−1
of
phosphate buffer (pH 7.0) and 2 mL of distilled water were
mixed in a vial of 10 mL with a screw cap. The preoxidation was initiated by the addition of 0.417 mL of 0.1 M
AAPH and carried out at 37 ◦
C water bath for 200 min
in the dark. The degree of oxidation was measured according to the thiocyanate (FTC) method [21] for measuring peroxides by reading the absorbance at 500 nm after
colouring with 0.1 mL of 0.02 mol L−1
ferrous chloride
in 3.5% (v/v) hydrochloric acid. A control was performed
with linoleic acid but without sample solution. Alphatocopherol (25µg mL−1
) was used as a positive control. All
the tests were performed in triplicate and the results were
averaged.