Synthesis of chitosan films for the quantification of Indigotine in candy samples by digital image analysis

Chitosan is a linear polysaccharide derived from the deacetylation of Chitin, which is the second most abundant polysaccharide found naturally, it’s present mainly in the exoskeleton of crustaceans¹. Due to some characteristics such as biodegradability, non-toxicity, high abundance, surface area and especially high adsorption, chitosan films are a great alternative for the removal of food dyes. Therefore, the aim of this work is to evaluate the making and usage of chitosan films for the adsorption of Indigotine as well as the quantification of this dye by digital image analysis. The chitosan films were prepared by the casting method proposed by Nga et al². Some parameters were studied such as surface area, pH, adsorption time, dye concentrations and buffer to evaluate the optimum parameters. The analytical signal was obtained by sticking the films on a paper and scanning it with a flatbed scanner to obtain the digital image. Hence, the image was treated using the software ImageJ in terms of RGB pixel frequency. This study showed that the analytical signal is higher when decreasing the surface area of the film. The best pH was 7,5 which is ideal for food samples, as sorption time increases it also increases the signal and it reaches an equilibrium in 90 min. The buffer phosphate/citric acid 0,1M was used. Lastly, a calibration curve and spiking curve were made, and it had nearly the same inclination coefficient, both with a reasonable good linearity as shown below.