2.6. Determination of antioxidant capacity (AC) by ABTS assay

This was performed according to the method of Re et al., (¹⁹⁹⁹). 5 ml of 7 mM solution of ABTS (2, 2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulphonic acid) (Sigma‐Aldrich) was mixed with 88 μl of 140 mM potassium persulfate solution as stock solution and allowed to stand in the dark for 16 hr at 29°C to generate the ABTS radicals. The working solution was prepared by adding to ABTS stock solution the phosphate buffer (75 mM, pH 7.4), to an absorbance of 0.7 ± 0.03 units at 734 nm using a UV‐visible spectrophotometer (Micronal, Model B582, São Paulo, Brazil). 190 µl of the resulting blue–green ABTS radical solution was added to 10 µl of wine sample. After 10 min of incubation in dark conditions, the absorbance was read at 734 nm. Trolox (6‐hydroxy‐2,5,7,8‐tetratmethylchroman‐2‐carboxylic acid) was used as an antioxidant standard to generate the standard curve. The experiment was performed in triplicate. The results were expressed as Trolox equivalent antioxidant capacity (mg TE·L⁻¹).