Total anthocyanins content (TAC)
Total anthocyanins content was determined using two samples containing 0.5 mL wine, 0.5 mL solution of 0.1% HCl in ethanol and 10 mL of 2% HCl aqueous solution. One sample was treated with 4.4 mL distilled water and the second with 4.4 mL of 13% sodium bisulfite solution and the mixture was diluted (1:1). Sample absorbance was determined at 520 nm using a blank solution prepared from 4.9 mL distilled water, 0.5 mL of 0.1% HCl in ethanol and 10 mL of 2% HCl aqueous solution. The differences (ΔA) between the absorbance value of sample prepared without sodium bisulfite and the absorbance value of sample prepared with sodium bisulfite were calculated. The anthocyanin content was express in mg/L of wine and was calculated by multiplying the ΔA value by 875 ( Ribéreau-Gayon, Glories, Maujean, & Dubordieu, 2006, chap. 6).