Folin-Chiocalteu colorimetric analysis using a scanner for rapid determination of total polyphenol content in many test samples

In order to develop a low cost method for rapidly determining the total amount of polyphenols in many samples, the colorimetric technique combined with the Folin-Chiocalteu (FC) method was investigated by using a digital scanner. Since the test solution containing polyphenols shows a blue-color after treatment of the FC method, the R-value was selected from RGB values of the digital image data obtained with a scanner. The absorbance which was calculated from the R-value was proportional to the concentration of a typical polyphenol such as chlorogenic acid and gallic acid. To discuss the cost performance of this colorimetric technique, the usual UV-Vis spectrophotometer method, the digital camera method and the micro-plate reader method were tested. As the linearity of a calibration curve obtained by the three methods was equivalent to that by the scanner method, the scanner method was decided to be the most effective technique from the standpoint of short measuring time and cost performance in the case of determination of the total polyphenol content in many samples. In the future, the FC-scanner method is likely to be multi-used at the site of functional food manufacturing.