Simple and Low-Cost Method for Quantifying Total Phenolic Compounds in Extra Virgin Olive Oils Using Digital Images

A simple, low-cost, and rapid analytical method for determination of the total phenolic content (TPC) in extra virgin olive oil samples (EVOOs) was developed, using digital images as an analytical tool. The method is based on an optimized Folin-Ciocalteu (F-C) colorimetric reaction, followed by digital image acquisition using a smartphone and processing with ImageJ® software to obtain red, green, and blue (RGB) values. The method was successfully validated, with recoveries between 73.11 and 112.65%, limits of detection (LOD) and quantification (LOQ) of 0.41 and 1.38 mg L-1, respectively. The TPC determined for eight EVOOs from different regions of the world were in the range of 186.38 to 378.87 mg gallic acid equivalent (GAE) kg-1, in accordance with some values reported in the literature. Statistical tests confirmed agreement between the results obtained using the digital image method and a reference method employing UV-Vis spectroscopy. The method complies with the principles of green chemistry, with reductions of cost, solvent use, and analysis time.