A Method Based on Digital Image Colorimetry for Determination of Total Phenolic Content in Fruits

In this study, a method based on digital image colorimetry was developed for the determination of the total phenolic content in fruits, using the Folin-Denis reagent after extraction procedure of the analytes. Phenolic compound extraction and experimental conditions adopted for the colorimetric reaction were established according to data reported in literature. The digital images of the chromogenic solutions were captured using an HD camera, stored in JPEG format, and analyzed based on the RGB color model. The conditions used to capture the digital images were optimized using multivariate methodology and the data obtained in the red channel were used as a chemometric response. Using the optimized conditions and form of processing the image data S = (255 - R), limits of detection and quantification were of 39 and 57 mg GAE 100 g(-1), respectively. Precision, estimated as relative standard deviation, was 1.4% for a guava pulp sample. The proposed method was applied to analyze different fruit samples (apple, guava, mango, pineapple, and strawberry) and the total phenolic content ranged from 245 to 703 mg GAE 100 g(-1). These results did not differ significantly from those obtained by UV-Vis spectrophotometry, at 95% confidence level.