Does anyone have a descriptive standard protocol for the total phenolic content assay with a reference?
In wine:
Folin-Ciocalteu’s method adopted from OIV Compendium (MA-E-AS2-10-INDFOL), using gallic acid as standard.
The method is based on the reduction of phosphomolybdic and phosphotungstic acids, present in Folin Ciocalteau reagent, by phenolics in the presence of sodium carbonate, forming blue products with maximum absorption close to 750 nm.
Briefly, 100 µL of wine/calibration standards are diluted 100 times adding the following reagents strictly in this sequence: 5 mL of distillate water, 0.5 mL of Folin–Ciocalteu reagent and 2 mL of 20% (w/v) sodium carbonate aqueous solution, bringing the volume to 10 mL with distilled water and mixed.
The mixture in then incubated at room temperature for 30 min, followed by absorbance measurement at 750 nm.
Range: 100-800 mg/L gallic acid equivalents.
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