Alginate/dye composite film-based colorimetric sensor for ammonia sensing: Chicken spoilage

In this study, Alginate (Alg)/Ca2+/dye composite films were fabricated using the solution casting method. The dyes used to include methyl red, phenol red, thymol blue, bromothymol blue, m-cresol purple, and bromocresol purple in the overall pH range of 4.4–9.6. The chemical composition and morphology of the Alg/Ca2+/dye composite films structure were investigated by Fourier transform infrared spectroscopy (FT-IR), filed emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The Alg/Ca2+/dye composite films were semi-transparent and mechanically flexible. The studied parameters include color volume, response time, recovery, reusability and drawing of the calibration curve along with statistical features including X‾, S, RSD, LOD, and LOQ. Colorimetric indicators used in the presence of pollutants (ammonia as the main pollutant released during spoilage of protein products) produce visible color changes to the naked eye. The observed changes are easily understood by consumers and non-experts.