Smartphone and Some Stickers Alert for Nitrite Levels in Food: Scientists

Many consumers have expressed their desire to minimize the amount of nitrites in their diet.  This has been in large part due to the scientific findings demonstrating an increased cancer risk of nitrite preservatives in processed meats*. If you are unfamiliar with the worldwide trend to minimize nitrite-preserved foods like processed meats, see the French government’s recent position on nitrite chemicals in processed meat and the link with colon cancer, and the World Health Organization unit known as the International Agency for Research on Cancer (IARC) position which put processed meat on its cancer list back in 2015.   The problem: Although many consumers want to limit consumption of these preservatives because the substances can form potentially cancer-causing compounds, knowing how much is in a food has been difficult to determine. Now, researchers have developed a color-changing film that consumers can stick onto foods and easily analyze nitrite levels by snapping a picture with a smartphone.

*Cured and processed meats, such as salami and bacon, are often treated with nitrite or nitrate salts to keep them looking and tasting fresh. Though nitrate is relatively stable, it can be converted to the more reactive nitrite ion in the body. When in the acidic environment of the stomach or under the high heat of a frying pan, nitrite can undergo a reaction to form nitrosamines, which have been linked to the development of various cancers. 



Some methods to determine nitrite levels in foods already exist, but they are expensive, require specialized equipment and are not very consumer-friendly. In order to redress this shortcoming, and help consumers make more informed decisions, scientists set out to develop an easy-to-use nitrite quantification system.


The research

To develop an easy-to-use nitrite quantification system, the researchers developed a film they called “POLYSEN,” which stands for “polymeric sensor,” made of four monomers and hydrochloric acid. Disks punched from the material were placed on meat samples for 15 minutes, allowing the monomer units and acid in the film to react with nitrite in a four-step azo coupling reaction. The disks were then removed and dipped in a sodium hydroxide solution for one minute to develop the color. When nitrite was present, the film’s yellowish hue deepened with higher nitrite levels in the food. To quantitate the color change, the researchers created a smartphone app that self-calibrates when a chart of reference disks is photographed in the same image as the sample disks.


The results

The research team tested the film on meats they prepared and treated with nitrite, in addition to store-bought meats, and found that the POLYSEN-based method produced results similar to those obtained with a traditional and more complex nitrite detection method. (In addition, POLYSEN complied with a European regulation for migration of substances from the film to the food.)

The researchers say their new application promises to be a user-friendly and inexpensive way for consumers to determine nitrite levels in foods.


What’s next

We are excited about this easy, new system to test for nitrite levels in food and look forward to learning when it will be ready for consumers.

Journal Reference:  Marta Guembe-García, Lara González-Ceballos, Ana Arnaiz, Miguel A. Fernández-Muiño, M. Teresa Sancho, Sandra M. Osés, Saturnino Ibeas, Jordi Rovira, Beatriz Melero, Cesar Represa, José M. García, Saúl Vallejos. Easy Nitrite Analysis of Processed Meat with Colorimetric Polymer Sensors and a Smartphone App. ACS Applied Materials & Interfaces, 2022; DOI: 10.1021/acsami.2c09467