A new smartphone app could warn users of carcinogenic chemicals in processed meats such as sausages, ham, bacon and salami.
Scientists in Spain have created a system that includes a color-changing film called “POLYSEN” that consumers can stick on meat products.
Labels turn darker when they detect high levels of nitrite, a meat preservative that can form potentially carcinogenic compounds.
Users can then take a picture of the film with a smartphone and a specially developed app will analyze the color and provide a nitrite concentration value.
Cured meats and processes, such as salami and pancetta, are often treated with nitrite or nitrate salts to keep them fresh in appearance and flavor (archive photo)
The graph of the researchers’ article shows that the system works. The discs perforated by the film are placed on meat samples for 15 minutes to allow them to react with the nitrites. The discs are then removed and immersed in a sodium hydroxide solution for one minute to develop the color. The higher the nitrite present, the deeper the yellowish tint of the film will be. A smartphone app self-calibrates when a reference disk table is photographed in the same image
HOW DOES THE “POLISI” WORK?
POLYSEN, or ‘polymeric sensor’, is a film composed of four monomers and hydrochloric acid.
The discs perforated by the film are placed on meat samples for 15 minutes to allow them to react with the nitrites.
The discs are then removed and immersed in a sodium hydroxide solution for one minute to develop the color.
The higher the nitrite present, the deeper the yellowish tint of the film will be.
A smartphone app self-calibrates when a chart of reference discs is photographed in the same image.
The system was created by experts from the Universidad de Burgos in Spain and detailed in a new study, published in ACS Applied Materials & Interfaces.
“There is a need to detect and control the different chemical compounds added to processed foods, such as processed meat,” they say.
“Our method represents a great advance in terms of analysis time, simplicity and orientation to use by average citizens.”
Cured meats and processed meats, such as bacon, hot dogs, ham, and sausages (including mortadella, an Italian dining meat), are often treated with nitrite or nitrate to keep them fresh and looking fresh.
Nitrites are widely used in processed meats to extend shelf life by warding off bacteria that can cause diseases such as salmonella, listeriosis, and botulism.
Basically, they also add a seductive, spicy taste and a pink hue to products like bacon, making them appear more appetizing.
Although nitrate is relatively stable, it can be converted into the most 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.
For this reason, consumers want to limit the consumption of these preservatives, but knowing how much there is in a food has been difficult to determine.
Nitrites add a seductive, tangy taste and fresh pink hue that seduces shoppers to products like sausages, ham, bacon, and salami (archive photo)
Here a worker packs slices of Mortadella, an Italian lunch of meat, in a factory (archive photo)
So the researchers created the new POLYSEN film – short for ‘polymer sensor’ – which is made up of four monomers and hydrochloric acid.
First, to create a “reference table,” the perforated discs from the film were placed on five different meat samples for 15 minutes, allowing the monomer units and acid in the film to react with the nitrite.
The meat samples all had different nitrite concentrations, so the researchers knew the discs would vary in color.
The discs were then removed and immersed in sodium hydroxide solution for one minute to develop the color.
The higher the nitrite in the meat, the deeper the yellowish hue of each film became.
To calibrate the system, film-perforated discs were placed on five different meat samples for 15 minutes, allowing the monomer units and acid in the film to react with the nitrite.
Next, the researchers created the smartphone app that uses colorimetry, which uses light to determine the concentration of particular compounds.
If photographed in the same image as the reference chart, the app can return a nitrite estimate for the sample disc.
The team tested the film on meats they prepared and treated with nitrite, as well as store-bought meats.
They found that the POLYSEN-based method produced results similar to those obtained with a traditional and more complex nitrite detection method.
Furthermore, POLYSEN complied with a European regulation for the migration of substances from film to food.
Although the team has only demonstrated the system for now, it could provide consumers with an easy-to-use and cost-effective way to determine nitrite levels in food in the future.
“This study is intended as a proof of concept in which the methodology has been shown to be practical and work,” they conclude.
NITRITES AND NITRATES: A PRIMER
Nitrites and nitrates are commonly used for seasoning meat and other perishable products.
They are also added to the meat to keep it red and give it flavor.
Nitrates are also found naturally in vegetables, with the highest concentrations in leafy vegetables such as spinach and lettuce.
It can also enter the food chain as an environmental contaminant in water, due to its use in intensive farming methods, livestock production and wastewater discharge.
Nitrites in food (and nitrates converted to nitrites in the body) can contribute to the formation of a group of compounds known as nitrosamines, some of which are carcinogenic, i.e. potentially carcinogenic.
In 2015, the World Health Organization warned that there were significant increases in the risk of bowel cancer from consuming processed meats such as bacon that traditionally have the addition of nitrites while being treated.
The current acceptable daily intake of nitrates, according to the European Food Safety Authority (EFSA), is 3.7 milligrams per kilogram of body weight per day.
EFSA’s acceptable daily intake of nitrites is 0.07 mg per kilogram of weight each day.