Dear,

Total phenolic concentration (TP) can be measured by the method described by Singleton and Rossi (1965). TP concentration can be expressed as mg gallic acid equivalents (GAE) 100 g−1 dry matter (DM) or mg GAE L−1 juice.

Best

Hello,

You can use this method. I always have good results.

Good luck!

Hi

you can use method from this article:

Singleton, v. l., orthofer, r. & lamuela-raventós, r. m. 1999. analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent. methods in enzymology. elsevier.

Antioxidants 2013, 2, 181-193; doi:10.3390/antiox2030181

www.mdpi.com/2076-3921/2/3/181/pdf