Using Colorimetric Polymer Sensors to Identify Nitrite in Prepared Meats

Using Colorimetric Polymer Sensors to Identify Nitrite in Prepared Meats

Nitrites and nitrate salts are commonly used to preserve cured and processed meats like salami and bacon. In the body, nitrate can be broken down into the more reactive nitrite. Nitrite can react with ammonia to produce carcinogenic nitrosamines. Nitrite levels in food can be determined with existing methods; however, these methods aren’t always user-friendly, and they sometimes necessitate the use of costly equipment and time-consuming procedures.

An easy-to-use nitrite measurement system was created by researchers at the University of Burgos in Spain, led by José M. Garca and Sal Vallejos. Polymeric sensor (or “POLYSEN” for short) is a colorimetric polymer film developed by the researchers. A bulk radical polymerization of four monomers (N-vinylpyrrolidone (VP), methylmethacrylate (MMA), 4-aminostyrene (SNH2), and N-(3-hydroxyphenyl)methacrylamide (HPMA)) in a molar ratio of 45:45:5:5, followed by an acid treatment with HCl, yielded the film.

After placing small discs constructed of the material on meat samples for 15 minutes, the nitrite in the samples reacted with the film’s components via an azo coupling process. After removing the discs, we immersed them in a solution of sodium hydroxide to make the colour permanent. In the presence of nitrite, the film’s characteristic yellowish colour turns brown. The researchers developed a mobile app to convert the colour shift into a nitrite concentration. The software auto-calibrates based on a chart of reference discs that were captured in the same picture as the sample disc.

The crew put the film through its paces using both homemade and commercially available nitrite-cured meats. The results of the devised method were found to be comparable to those of a standard nitrite detection technique. Researchers believe their method could give people an accessible and low-cost option for checking the nitrite content of foods.

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