Quantification of the Food Dye Indigo Carmine in Candies Using Digital Image Analysis in a Polyurethane Foam Support

Abstract

The aim of this present work was to propose an alternative methodology to quantify the food dye indigo carmine in industrialized candies by the innovative technique of digital image analysis. To do so, the candy was solubilized in water and extracted to polyurethane foam, which is capable of selectively adsorbing the dye, removing interferents from the matrix. The foam was dried and glued on a sheet of paper. After that, digital images of the system were taken using a flatbed scanner. A free-access software was used to treat these images in order to obtain the color intensity of the foam, which was related to the concentration of the analyte. The linear range of this proposed method was 0.1 to 5.0 mg L−1. The limits of detection and quantification were respectively 0.20 μg g−1 and 0.68 μg g−1. These limits were adequate to determine indigo carmine in the studied candies. The precision of the method was estimated in 2.16% by the standard deviation of daily replicates and the accuracy in 113 ± 2% by recovery tests. The method was applied in the quantification of the analyte in real samples, and these results were compared with the ones obtained by a previously established chromatographic method, resulting in a statistical conformity at 95% confidence level.