2.6.4. Reducing power
Reducing power was determined according to the method proposed
by Oyaizu (1986). Stock solutions were diluted as described
for FRAP. A 500 L sample solution was mixed with 1.25 mL of 0.2 M
phosphate buffer (pH 6.6) and 1.25 mL of 1.0% (w/v) potassium ferricyanide.
The resulting mixture was incubated at 50 ◦C for 30 min.
After the addition of 1.25 mL of 10% (w/v) trichloroacetic acid, the
mixture was centrifuged at 2500
×
g for 10 min. A 2.5 mL supernatant
was mixed with water (2.5 mL) and 0.5 mL of 0.1% (w/v)
ferric chloride before the absorbance was determined at 700 nm.