Quantification of the Food Dye Indigo Carmine in Candies Using Digital Image Analysis in a Polyurethane Foam Support Igor Coreixas de Sá 1 & Fernanda Neves Feiteira 1 & Wagner Felippe Pacheco 1 Received: 16 August 2019 /Accepted: 27 January 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020 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 μgg -1 and 0.68 μgg -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. Keywords Food coloring . Indigo carmine . Candies . Polyurethane foam . Digital image analysis Introduction Although the consumption of food should depend mainly on its nutritional value, its color, aroma, and texture are factors that exert a stimulating or inhibiting effect on human appetite (Bobbio and Bobbio 2003). Notwithstanding these are asso- ciations inherent to psychological patterns; they interfere in the choice of products. Hence, food industries extensively employ food colorants to make their products more apprecia- ble (Price et al. 1978) (Fig. 1). At the beginning, the majority of colorants were only nat- ural. However, the use of synthetic dyes has increased in time due to its better coloring capacities when compared with the natural ones. Moreover, there are many other aspects that stand out, such as high stability in terms of pH, light, and oxidation; low cost; and antimicrobial resistance. The disadvantage of the use of artificial colorants lies main- ly in the fact that they are a class of nonnutritive additives, introduced into food and beverages for the sole purpose of conferring color. In addition, several studies have demonstrat- ed its toxicity (Walthall and Stark 1999), carcinogenic poten- tial (Price et al. 1978), mutagenicity (Tsuda et al. 2001), and the occurrence of hyperactivity disorders in children (Food and Drug Administration/Center for Food Safety and Applied Nutrition 2011). This suggests that whether these dyes cannot be eradicated completely, they should be at least controlled. Indigo carmine (IC) is an artificial dye extensively used in some countries as food coloring. The acceptable daily intake (ADI) of it is 5 mg/kg body weight, according to the European, American, and Brazilian food legislations (Comissão Nacional de Normas e Padrões para Alimentos 1977; EFSA 2014; Ferber 1987). Its excessive consumption can lead to behavioral disorders, as well as respiratory prob- lems, allergies, nausea, vomiting, and hives (Ferber 1987). Some methods have been proposed to quantify dyes in food matrices, based mainly on electrochemical techniques (Arvand et al. 2017; Deroco et al. 2018; López-de-Alba et al. 2002; Sierra-Rosales et al. 2017), chromatography (Alves et al. 2008; Floriano et al. 2018; García-Falcón and Simal-Gándara 2005), UV Vis spectrometry (Berzas Nevado et al. 1998; Ni and Gong 1997; Pourreza and Ghomi 2011; Tikhomirova et al. 2017), chemometrics (Botelho et al. 2017; * Wagner Felippe Pacheco wfpacheco@id.uff.br 1 Fluminense Federal University, Niterói, Rio de Janeiro, Brazil Food Analytical Methods https://doi.org/10.1007/s12161-020-01715-5