Abstract:

Folin-Ciocalteu colorimetric assay for polyphenols extracted from apple pomace by supercritical CO2 extraction using gallic acid as reference substance was systematically investigated for developing an optimal colorimetric method for the determination of polyphenols in apple pomace. The optimum colorimetric conditions were determined as follows: 0.3 mL of Folin- Ciocalteu reagent, 1.5 mL of saturated Na2CO3 solution, 20 min of reaction time and 25－35 ℃ of reaction temperature. The calibration curve for quantifying polyphenols exhibited a good linearity in the range of 1－10 μg/mL (r = 0.9994). The average recoveries of gallic acid at high, medium and low spike levels were 99.66%, 98.79% and 98.20% (n = 5), respectively, which were reaveraged at 98.82%, with a RSD of 1.93%. The proposed method demonstrates the advantages of rapidity as well as high accuracy and reproducibility.

Key words: polyphenols, Folin-Ciocalteu colorimetry, apple pomace, supercritical CO2 extraction