Desenvolvimento de etiqueta inteligente com indicador colorimétrico para identificação de SO2 em crustáceos

Abstract

Sulfating agents are widely applied to shrimp as conservatives and sulfur dioxide (SO2) is produced from the degradation if these agents. Due to toxicological issues associated to the ingestion of food conserved with sulfites, the Brazilian legislation predicts the limit of 100 ppm of residual SO2 in crustaceans. This study had the objective of developing an intelligent label with SO2 indicator. The indicator label was developed from starch films incorporated with iodine by the casting technique. The work was divided into three stages, with the first regarding the production of labels and their concerning thickness, solubility in water, Fourier Transform Infrared Spectroscopy (FTIR), ther mogravimetric analysis (TGA), Differential Scan Calorimetry (DSC), Scanning Electron Microscopy (SEM), X-Ray Energy Dispersing Spectroscopy (EDS) and Color Analysis. The micrographs and EDS analyses showed uniformity of the polymeric matrix, while the remaining properties of the label were altered by the addition of iodine (I2) to the matrix. In the second stage, the labels were exposed to 15 minutes to solutions with different concentrations of SO2 under two temperature conditions (-18 C and 4 C), being posteriorly analyzed by FTIR and regarding parameters of color L* (Luminosity), h* (tone), dE* (total color difference). Parameters L*, h* and dE* were higher in the temperature of 4 C. The values for L* and h* were reduced with the increase of the concentration of iodine, while for dE*, this effect was not significant. When placing the labels in contact with the SO2 solutions, L*, h* and dE* increased with the increase in the contents of SO2, and the chemical structure of the labels changed with the exposure to SO2. In the third stage, the labels were tested in shrimp, in three concentrations of SO2 (100, 110 and 120 ppm) and characterized regarding the parameters of color L*, C* (Saturation), h*, dE* and transparency. The highest concentration of SO2 promoted higher values for L* and dE*, and lower values for C*, while for h*, there was no significant influence. Concentrations higher than 100 ppm produced higher values for transparency. The obtained results were promising given that the intelligent labels showed good indicators for the concentration of SO2 by means of change in the coloration from dark blue/black to colorless in the time of 15 minutes.