A rapid estimation of pigment content in virgin olive oils by a solvent-free method

In this work, a fast method was proposed for estimating the virgin olive oils (VOOs) carotenoids and chlorophylls concentration using color measurement. The pigment content by conventional spectrophotometry method and CIELAB color (L*, a*, and b*) at different degree of sample thickness (from 5 to 50 mm) of one hundred VOOs were measured. Oil carotenoids and chlorophylls content were correlated with the color parameters for the different oil thickness studied to design the prediction models of the new method. The best regression coefficients (R-2) were obtained for multiple linear regression model using the three independent variables (L*, a*, and b*) together measured at 5 mm of oil thickness. The R-2 were 0.9679, 0.9515, and 0.9644 for predicting carotenoids, chlorophylls, and total pigments, respectively. External validation of these prediction models was satisfactory (relative error < 0.1). Therefore, this new solvent-free colorimetric method is a useful method for determination of carotenoids and chlorophylls content in VOOs.

Automated summary

This study proposes a fast method for estimating the concentration of carotenoids and chlorophylls in virgin olive oils (VOOs) using color measurement. The pigment content of 100 VOOs was measured using conventional spectrophotometry method and CIELAB color parameters (L*, a*, and b*) at different oil thicknesses. The color parameters were correlated with the carotenoids and chlorophylls content to develop prediction models. The best regression coefficients (R-2) were achieved using multiple linear regression with the three independent variables measured at 5 mm of oil thickness, with R-2 values of 0.9679, 0.9515, and 0.9644 for carotenoids, chlorophylls, and total pigments prediction, respectively. The prediction models showed satisfactory external validation (relative error < 0.1). Therefore, this new solvent-free colorimetric method is useful for determining the carotenoids and chlorophylls content in VOOs.