Thiobarbituric acid (TBA) method
The method described by Ottolenghi (1959) was used to determine
the TBA values of the samples, with slight modifications as
described by Zahin, Aqil, and Ahmad (2009). Aliquots of 2 mL of
20% trichloroacetic acid and 2 mL of 0.67% TBA aqueous solution
were added to 1 mL of the sample solution prepared as in FTC procedure
and incubated in a similar manner. The mixture was placed
in a boiling water bath for 10 min. After cooling, the solution was
centrifuged at 1900g for 20 min, and the absorbance of the supernatant
was measured at 532 nm. Antioxidant activity was based on
the absorbance of the final day. The percentage of antioxidant
activity was calculated using the equation that was used to calculate
the antioxidant activity in the FTC method.