Aliquots of 1 mL of the phenolic extract
mixed 4.5 mL of an alkaline solution (Na2CO3 4%, CuSO4.4H2O 2%
and KNaC4H4O6 4%, 100:1:1), were incubated for 15 min at
40 C. After this, 0.5 mL of Folin–Ciocalteau (Qell, diluted 1:2)
was added, left for 10 min at room temperature, and readings were
performed at 750 nm using a spectrophotometer. The phenolic
content in the samples was estimated using feluric acid (Sigma, Japan)
as standard (2–20 lg/ml), and its content increase with the
fermentation was calculated according to Eq.