Improper freezing of food causes food waste and negatively impacts the environment. Now, a team of researchers from the Istituto Italiano di Tecnologia (Italian Institute of Technology) has developed a food-grade device from edible materials that can detect whether your frozen food has thawed and then been refrozen – and is, therefore, potentially contaminated.
The proof-of-concept sensor consists of a small beeswax chamber containing table salt and red cabbage. It provides a color readout when it’s warmed above a specific temperature.
The researchers started by building a device that generated an electrical current as it defrosted, connecting magnesium and gold electrodes through an electrolyte solution held in a plastic container. The team tested the device with solutions of frozen edible electrolytes, including table salt and calcium-containing salts, and naturally electrolyte-rich foods, including a grape, melon, and apple.
As the solutions defrosted, they conducted current between 0º C to -50º C (32º F to -58º F), which the researchers say could be fine-tuned based on the amount and identity of the salt.
Next, this edible, self-powered temperature sensor was connected to a color-changing system containing tin and gold electrodes and red cabbage juice that produced an irreversible shift from reddish purple to blue when the current was applied.
In the final step, researchers put all of the parts together in a block of beeswax that held the temperature-activated and indicator solutions in separate chambers. And they demonstrated that the self-powered device could be used for frozen food monitoring. The researchers say that their proof-of-concept sensor paves the way for edible materials to be used in inexpensive, safe technologies that alert customers to a frozen product’s storage history.
- Ivan K. Ilic, Leonardo Lamanna, Daniele Cortecchia, Pietro Cataldi, Alessandro Luzio, and Mario Caironi. Self-powered edible defrosting sensor. ACS Sensors, 2022; DOI: 10.1021/acssensors.2c01280