Scientists develop cork-based sensor to detect sodium nitrite in beverages

Scientists in Brazil have developed a sensor that can identify sodium nitrite (NaNO2) in various beverages, such as mineral water, orange juice, and wine. The ingredient is used as a preservative and color fixative in foods, and can form carcinogenic compounds like nitrosamines, posing potential health risks to consumers.

The team at the Federal University of São Carlos (UFSCar) in the state of São Paulo developed the low-cost device by using pieces of natural cork with the same material used in wine stoppers.

Spotting even tiny amounts of sodium nitrite is important for food safety and quality control. “Detection [of NaNO2] in beverages, especially wines, is important for quality control, since its use is not legally permitted in Brazil and most countries,” note the authors.

Sodium nitrite helps retain the pink and red color in ham, sausages, and bacon. However, the potential links to cancer motivated the team to develop a “simple, fast, and accessible way to detect the compound and ensure the quality and safety of liquid consumption,” says Bruno Campos Janegitz, head of the Laboratory of Sensors, Nanomedicine, and Nanostructured Materials (LSNano) at UFSCar. 

According to the researcher, the LSNano projects aim to use materials from low-cost platforms that provide added value while respecting the environment. In this study, the team chose it as the starting point because it is lightweight, natural, and inexpensive.

The study, published in the journal Microchimica Acta, explores cork-based electrochemical sensors as a “green alternative” for sodium nitrite detection in beverage samples.

“The results of this study reinforce the potential of cork as a sustainable substrate for high-performance electrochemical sensors, a viable and promising alternative for food analysis, replacing less eco-friendly conventional substrates,” reads the study.

Tapping cork sensor for beverage safety

To develop the sensor, the scientists used lasers to burn patterns into the cork, turning its surface into graphene — a highly conductive form of carbon. This makes the cork act like a tiny electrical sensor that can pick up the presence of sodium nitrite.

They then coated the device to protect it from liquids and tested it in different drinks. It showed high sensitivity and accuracy, detecting nitrite at concentrations “compatible with those relevant to food and environmental safety,” notes the study. 

“This process is sustainable, doesn’t require toxic reagents, and results in a highly conductive material, which is essential because nitrite undergoes well-known electrochemical oxidation. Therefore, we need a highly conductive sensor to detect the compound,” Janegitz explains.

The project is still being tested in the lab, and the device’s design still needs improvements for practical use, note the researchers.