The antioxidant activity of the natural extract was determined by the
DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method
described by von Gadow, Joubert, and Hansmann (1997), with slight
modifications. Sample solutions of the natural extract samples collected
at selected times after exposure to temperature, according to the conditions
indicated in Section 2.3.1, were prepared in methanol. Two synthetic
compounds with antioxidant properties and commonly used in
the food industry, BHA and BHT, were used as controls. An aliquot of
each antioxidant (50 μl) was added to 2 ml of DPPH radical methanolic solution (3.6 × 10−5M), shaken vigorously in a vortex and left to stand
in the dark at room temperature. The absorbance was measured at
515 nm in a spectrophotometer, after 16 min at room temperature. All
determinations were made in triplicate. The decrease in absorbance
was converted to percentage of DPPH inhibition (IP), according to the
following equation: