Colorimetric sensor based on a poly(ortho-phenylenediamine-co-aniline) copolymer for the monitoring of tilapia (Orechromis niloticus) freshness

For monitoring tilapia (Orechromis niloticus) freshness degree, a colorimetric method based on a copolymer of ortho-phenylenediamine and aniline, in a molar ratio of 1 to 1, was developed. The optical sensor changes color as a function of pH, therefore, it is sensitive to the presence of alkaline vapors such as the volatile amines (TVB-N) produced during fish spoilage. A kinetic approach was used to correlate the copolymer (sensor) response to the presence of ammonia, dimethylamine, and trimethylamine vapors, which are the main products generated by the bacteria during fish spoilage. The levels of TVB-N and microbial growth patterns (Pseudomonas spp), in specimens of tilapia fillets stored under refrigeration at 10 degrees C, correlated well with the color change of the copolymer, showing that after 48h the specimen was no longer fit for human consumption. (c) 2017 Elsevier B.V. All rights reserved.