A new smartphone app could alert users to cancer-causing chemicals in processed meats like sausages, ham, bacon and salami.
Scientists in Spain 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 nitrites, meat preservatives that can form potentially carcinogenic compounds.
Users can then take a picture of the film with their smartphone, and a specially designed app will analyze the color and give a reading of the nitrite concentration.
Cured and processed meats such as salami and bacon are often treated with nitrite or nitrate salts to keep them looking fresh and flavorful (file photo)
A graphic from the researchers’ article shows how the system works. Disks, knocked out of the film, are placed on the meat samples for 15 minutes to allow them to react with nitrite. The discs are then removed and immersed in sodium hydroxide solution for one minute to develop the color. The higher the nitrite content, the deeper the yellowish tint of the film. The smartphone application performs self-calibration when the reference disk table is photographed on the same image.
HOW POLYSEN WORKS?
POLYSEN, or “polymer sensor”, is a film consisting of four monomers and hydrochloric acid.
Disks, knocked out of the film, are placed on the meat samples for 15 minutes to allow them to react with nitrite.
The discs are then removed and immersed in sodium hydroxide solution for one minute to develop the color.
The higher the nitrite content, the deeper the yellowish tint of the film.
The smartphone app performs self-calibration when a table of reference discs is photographed on the same image.
The system was created by experts from the University of Burgos in Spain and is detailed in a new study published in Application materials and interfaces ACS.
“There is a need to detect and control the various chemicals added to processed foods such as processed meats,” they say.
“Our method represents a big step forward in terms of analysis time, simplicity, and focus on use by ordinary citizens.”
Cured and processed meats such as bacon, hot dogs, ham, and sausages (including mortadella, an Italian breakfast meat) are often treated with nitrites or nitrates to keep them looking fresh and flavorful.
Nitrites are widely used in processed meats to extend their shelf life by protecting against bacteria that can cause diseases such as salmonellosis, listeriosis and botulism.
Importantly, they also add an attractive tangy flavor and pink hue to foods like bacon, making them more appetizing.
Although nitrate is relatively stable, it can be converted in the body to the more reactive nitrite ion.
In the acidic environment of the stomach or when the pan is very hot, nitrite can react to form nitrosamines, which are associated with the development of various types of cancer.
For this reason, consumers want to limit their intake of these preservatives, but it is difficult to determine how much of them a food contains.
Nitrites give an attractive tangy flavor and a seductive pink hue to foods such as sausages, ham, bacon and salami (file photo)
Here, a worker packs pieces of mortadella, Italian lunch meat, in a factory (file photo)
So the researchers created a new film, POLYSEN, an acronym for “polymer sensor,” which is made up of four monomers and hydrochloric acid.
First, to create a “reference table”, discs cut from the film were placed on five different meat samples for 15 minutes, which allowed the monomer units and acid in the film to react with nitrite.
All the meat samples had different concentrations of nitrite, so the researchers knew that the discs would vary in color.
The disks were then removed and immersed in a sodium hydroxide solution for one minute to develop the color.
The higher the nitrite content of the meat, the deeper the yellowish tint of each film became.
To calibrate the system, discs punched out of 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 researchers then created a smartphone app using colorimetry, which uses light to determine the concentration of certain compounds.
When photographed on the same image as the reference chart, the application can return the nitrite estimate for the sample disk.
The team tested the film on meat they prepared and treated with nitrite, in addition to store-bought meat.
They found that the POLYSEN-based method gave results similar to those obtained with the traditional and more sophisticated nitrite detection method.
In addition, POLYSEN complies with European standards for the transfer of substances from film to food.
The team has only demonstrated the system so far, but in the future it may provide consumers with a convenient and inexpensive way to determine nitrite levels in foods.
“This study is intended to be a proof of concept in which it has been demonstrated that the methodology is practical and works,” they conclude.
NITRITE AND NITRATE: GROUND MATERIAL
Nitrites and nitrates are commonly used to preserve meat and other perishable foods.
They are also added to meat to keep it red and add flavor.
Nitrates are also found naturally in vegetables, with the highest concentrations found 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, animal husbandry and wastewater disposal practices.
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, meaning they can cause cancer.
In 2015, the World Health Organization warned of a significant increase in the risk of bowel cancer when eating processed meats such as bacon, which traditionally has nitrites added during processing.
The current tolerable daily intake of nitrates, according to the European Food Safety Authority (EFSA), is 3.7 milligrams per kilogram of body weight per day.
The allowable daily intake of nitrites set by the EFSA is 0.07 mg per kilogram of body weight each day.