4.4.2. Estimation of Total Phenolic Content Using the Folin-Ciocalteu Method

Total phenolic content in the samples was determined according to the Folin-Ciocalteau method [105]. This colorimetric method is based on the reduction of the phosphotungstic-phosphomolybdenum acid complex, creating a blue chromophore. Maximum absorption of the chromophores depends on the alkaline solution and the concentration of phenolic compounds, with a more intense blue color indicating higher absorption and concentration of antioxidants [106].

In a tube, 40 µL of diluted extract sample, 3.16 mL of distilled water, and 0.2 mL FC reagent were added and vortexed. After 3 min, 0.6 mL of aqueous sodium carbonate (20%) were added, the sample was vortexed again and placed in a water bath at 40 °C. After 30 min, the absorbance was read, at 765 nm. Total phenol concentration was calculated from the calibration curve, where gallic acid was the standard. Results were expressed as mg of gallic acid per g of dried fruit matter (seeds excluded) [24].