Toward a fully edible sensor showing if frozen food has previously thawed

Toward a fully edible sensor showing if frozen food has previously thawed
A proof-of-concept sensor designed from edible materials produces a visible color change (seen in the right circle) as a piece of frozen pork thaws. Credit: Adapted from ACS Sensors 2022, DOI: 10.1021/acssensors.2c01280

When you're standing in the frozen food aisle, it's nearly impossible to know whether that Salisbury steak has thawed and refrozen—a process with potentially harmful consequences. So, researchers reporting in ACS Sensors have designed a food-grade device from edible materials, including table salt, red cabbage and beeswax, that lets you know. The proof-of-concept sensor provides a color readout when it's warmed above a specific temperature, which is tunable from -58 F to 32 F.

Keeping food cold while it's transported and stored is essential to retaining its flavor and quality, reducing the risk of food poisoning and minimizing waste. While researchers have developed devices that alert manufacturers when cold items are exposed to unwanted temperatures, they only indicate changes above freezing. To create a sensor for frozen products, one could be to use materials with that are altered upon melting. It would also be ideal if such changes could produce a signal, such as a visible color change. In addition, an edible electronic device, which uses only food and consumable components, would be the safest way to monitor food. So, Ivan Ilic, Mario Caironi and colleagues set out to develop the first fully edible, self-powered temperature sensor with a visible color indicator for use with frozen products.

The researchers started by building a device that generated an as it defrosted, connecting magnesium and gold electrodes through an held in a plastic container. They tested the device with solutions of frozen edible electrolytes, including and calcium-containing salts, and naturally electrolyte-rich foods, including a grape, melon and apple. As the solutions defrosted, they conducted current between -58 F and 32 F, which the researchers say could be fine-tuned, based on the amount and identity of the salt. Next, this device was connected to a color-changing system, containing tin and gold electrodes and juice, that produced an irreversible shift from reddish purple to blue when current was applied.

  • Self-powered edible defrosting sensor
    Researchers at IIT-Istituto Italiano di Tecnologia (Italian Institute of Technology) have developed the first self-powered defrosting sensor that may be used in future to detect improper freezing of food while the sensor is placed on it. The new device has been described in an article published in ACS Sensors journal on October 12, 2022. The sensor is fully edible, as it exploits the inherent electronic properties of commonly ingested liquids or supplements, such as water, table salt, and various electrolytes. The device is composed of two parts: a galvanic cell, operating with an aqueous electrolyte solution that generates an electrical current when defrosted; and a color-changing system indicator, based on red cabbage juice, producing an irreversible shift from reddish purple to blue when the galvanic cell produces the current. A block of beeswax keeps the two parts bound together. The temperature at which the sensor reacts can be tuned between 0 and −50 °C by changing salts or its concentration in water.Researchers, including Ivan Ilic, working in a team coordinated by Mario Caironi at IIT's Center for Nano Science and Technologies in Milano (Italy), believe that this proof of concept could pave the way for an inexpensive and safe technology to be largely exploited in the food and drug cold supply chains, reducing wastes and improving safety. The research study had been supported by a grant from European Research Council. Credit: IIT-Istituto Italiano di Tecnologia
  • Self-powered edible defrosting sensor
    Credit: IIT-Istituto Italiano di Tecnologia

In the final step, the team put all of the parts together in a block of beeswax that held the temperature-activated and indicator solutions in separate chambers, and 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.

More information: Self-Powered Edible Defrosting Sensor, ACS Sensors (2022). DOI: 10.1021/acssensors.2c01280

Journal information: ACS Sensors

Citation: Toward a fully edible sensor showing if frozen food has previously thawed (2022, October 12) retrieved 8 December 2023 from
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