2.5.3. Total phenolics
Total phenolics (TP) were determined by the colorimetric method
described by Singleton, Orthofer, and Lamuela-Raventós (1998) using
the Folin–Ciocalteu reagent. A portion of 0.5 mL of broccoli juice was
mixed with 0.5 mL of Folin–Ciocalteu reagent and 10 mL of saturated
Na2CO3 solution. Samples were kept at room temperature in darkness
for 1 h. Afterwards, the absorbance was measured at 725 nm using a
CECIL 2021 spectrophotometer (Cecil Instruments Ltd., Cambridge,
UK). Concentrations were determined by comparing the absorbance of
the samples with a calibration curve built with gallic acid. The results
were expressed as mg of gallic acid per 100 mL of juice.