The content of total polyphenolic compounds in gingko wine
and the typical Chinese liquors was determined using the Folin–
Ciocalteu reagent (Paixão et al., 2007; Zhang et al., 2010). Briefly,
1 mL of wine sample was put into a 15 mL test tube containing
5 mL of deionized water. 1 mL of Folin–Ciocalteu reagent and
3 mL of 20% Na2CO3 solution was added in the tube and mixed
thoroughly. After standing in dark place at room temperature for
30 min, the absorbance of the mixture was measured at 760 nm
using a 7200 spectrophotometer (UNICO (Shanghai) Instruments
Co., Ltd). All results were compared to the standard curve of gallic
acid which was prepared at a concentration range from 0 to
500 mg/L and expressed as gallic acid equivalent (mg GAE/L wine).
Each sample was performed in triplicate.