Easy Nitrite Analysis of Processed Meat with Colorimetric Polymer Sensors and a Smartphone App

We have developed an in situ methodology for determining
nitrite
concentration in processed meats that can also be used by unskilled
personnel. It is based on a colorimetric film-shaped sensory polymer
that changes its color upon contacting the meat and a mobile app that
automatically calculates the manufacturing and residual nitrite concentration
by only taking digital photographs of sensory films and analyzing
digital color parameters. The film-shaped polymer sensor detects nitrite
anions by an azo-coupling reaction, since they activate this reaction
between two of the four monomers that the copolymer is based on. The
sensory polymer is complemented with an app, which analyzes the color
in two different digital color spaces (RGB and HSV) and performs a
set of 32 data fittings representing the concentration of nitrite
versus eight different variables, finally providing the nitrite concentration
of the test samples using the best fitting curve. The calculated concentration
of nitrite correlates with a validated method (ISO 2918: 1975) usually
used to determine nitrite, and no statistically significant difference
between these methods and our proposed one has been found in our study
(26 meat samples, 8 prepared, and 18 commercial). Our method represents
a great advance in terms of analysis time, simplicity, and orientation
to use by average citizens.