Hot dogs, processed meats on tray

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BURGOS, Spain — Trying to avoid overly-processed beef for your next barbecue? A new smartphone app is able to check your meat for preservatives that lead to cancer-causing chemicals before you eat them.

Scientists have developed a color-changing film shoppers can stick onto processed meats. Snapping a picture quickly analyzes levels of preservatives known as nitrates and nitrites. They give sausages and bacon their characteristic pink hue and distinctive flavor, but can form tumor-triggering compounds. The more there, are the darker the image.

People are advised to limit nitrite consumption. Knowing how much is in a product has been difficult to determine, until now.

“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 authors write.

Their paper is published in the journal ACS Applied Materials & Interfaces.

Cured and processed meats also include ham, pâtés and salami. They are 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,” the researchers explain. “Some methods to determine nitrite levels in foods already exist, but they are not very consumer-friendly and often require expensive and laborious techniques and instruments.”

The device is easy-to-use and helps consumers make more informed decisions. It has been named “POLYSEN” for “polymeric sensor.” It is made of four monomers and hydrochloric acid. Discs punched from the material were placed on meat samples for 15 minutes, enabling the film to react with nitrite. The discs were then removed and dipped in a sodium hydroxide solution for one minute to develop the color. When nitrite is present, the film’s yellowish hue deepened with higher nitrite levels in the food.

Nitrite-detection discs
The darker the yellowish hue of the discs, the higher the concentration of nitrite in the food. (Credit: Adapted from ACS Applied Materials & Interfaces 2022, DOI: 10.1021/acsami.2c09467)

To quantify the color change, the researchers created a smartphone app that self-calibrates when a chart of reference discs is photographed in the same image. The team tested the film on meats they prepared and treated with nitrite, in addition to store-bought meats. The POLYSEN-based method produced results similar to those obtained with a traditional and more complex nitrite detection technique.

In addition, POLYSEN complied with a European regulation for migration of substances from the film to the food. The researchers say the new approach could provide a cheap alternative to other devices.

“Our method represents a great advance in terms of analysis time, simplicity, and orientation to use by average citizens,” the authors conclude.

South West News Service writer Mark Waghorn contributed to this report.

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