A graduate student at Southern Methodist University (SMU), has developed a miniature pH sensor that can detect when food has spoiled in real-time. 

The 2-millimeter long and 10-millimeter wide flexible pH sensor is designed to be incorporated into food packaging, such as plastic wrapping. Traditional pH meters are too bulky to be included in every package of food to monitor freshness in real-time.

“The pH sensors we developed work like a small wireless radio-frequency identification device – similar to what you find inside your luggage tag after it has been checked at airports or inside your SMU IDs. Every time a food package with our device passes a checkpoint, such as shipping logistics centers, harbors, gates, or supermarkets’ entrances, they could get scanned and the data could be sent back to a server tracking their pH levels,” Khengdauliu Chawang, graduate student and lead creator of the device, said.

Food waste is a significant issue, with roughly 40 percent of food in the United States going uneaten and 1.3 billion metric tons of food produced worldwide going to waste every year, according to estimates by the Food and Agriculture Organization of the United Nations and Feeding America estimates. Chawang’s invention is a disposable and cost-effective way to detect freshness levels and prevent food waste, which can contribute to food insecurity and lost profits for manufacturers.

The pH level in food is directly linked to its freshness. High pH levels, for example, indicate spoiled food as fungi and bacteria thrive in such environments. The pH sensor developed by Chawang detects the electrical charge generated by the concentration of hydrogen ions inside food to convert it to pH values. The sensor is made with biocompatible materials and printed on flexible films, which makes it inexpensive and disposable.

Chawang was awarded the Best Women-owned Business Pitch at the 2022 Institute of Electrical and Electronics Engineers (IEEE) Sensors Conference for her invention. The sensor has successfully been tested on various food items, such as fish, fruits, milk, and honey. The electrode device developed for monitoring food could also be used to ensure reliable fermentation for cheese and wine. The technology could have potential applications in detecting early warning signs of sepsis or wound infection when used on the skin.

About SMU

Southern Methodist University is a globally recognized research university located in Dallas. It has over 12,000 students in eight degree-granting schools.

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