The nose knows: Electric schnoz can smell when your food’s gone bad - Berkeley News

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The nose knows: Electric schnoz can smell when your food’s gone bad

A new proof-of-concept device created by UC Berkeley researchers can sniff out gases emitted by harmful bacteria, allergens and other food safety hazards.

By Kara Manke

An “electronic nose” created by UC Berkeley researchers can detect the gases produced by spoiled food and food allergens better than human noses.

Brandon Sánchez-Mejia/UC Berkeley

June 17, 2026

Most of us have used the sniff test to decide whether a slightly expired bottle of milk or a week-old box of takeout is still good to eat. But while the human nose can be quite astute, it doesn’t always catch everything. Each year, millions of people in the U.S. are sickened by food-borne pathogens that thrive in undercooked or spoiled food.

Luckily for our collective stomachs, a new “electronic nose” developed at UC Berkeley can detect the scents associated with spoiled food much more accurately than the human nose. It can also sniff out the presence of common food allergens, like walnuts and peanuts, which can be deadly for those with sensitivities. The nose is described in a new study published today (June 17) in the journal Science Advances.

“I think ‘smart’ fridges — which come with sensors that you can control on your phone — would be a great application for this kind of technology,” said study lead author Carla Bassil, a Ph.D. student in electrical engineering and computer sciences at Berkeley and a member of the Javey Research Group. “How great would it be if your fridge could tell you, ‘Hey, your broccoli’s going to go bad soon, so you should probably eat that’? Or, ‘Your chicken is on its last day’?”

Carla Bassil is a fourth year Ph.D. student in electrical engineering and computer sciences at UC Berkeley and a member of the Javey Research Group. Brandon Sánchez-Mejia/UC Berkeley

The new artificial schnoz nose is made up of an array of 16 tiny gas sensors, each of which is sensitive to a slightly different combination of gaseous compounds.

“You can think of it like a set of digital taste buds, where each sensor on this chip responds uniquely to the various gas molecules presented to it,” Bassil said in a UC Grad Slam talk about her research. “Each of these 16 sensors has a different sensing film on it, and it works by converting chemical reactions between the sensor surface and the gas molecule into electrical signals.”

Using machine learning, Bassil trained a model to recognize the sensor response profiles associated with seven different foods: strawberry, blueberry, banana, walnut, hazelnut, cashew and peanut. She also trained it to recognize the scent of raw chicken, milk and eggs when they were fresh and when they had been left out at room temperature for 24 hours and 48 hours.

Bassil found that the nose was sensitive enough to smell 0.05 grams of isolated walnut, which is about one hundredth of an average shelled walnut. However, she has yet to test the sensitivity of the device in environments where other gases are present, such as when walnuts are in a salad or a cake, or when spoiled food is in a refrigerator with other foods.

“The idea is that we can use the relative selectivity of the gas sensors, paired with the pattern recognition abilities of machine learning, to sort out which gas fingerprint is associated with each food,” Bassil said. “The result is a sensor chip that is far more sensitive and far more objective than any human nose can be.”

The electronic nose contains 16 different gas-sensitive materials (small circles in the center) that each react to the gas molecules presented to it (left). The device records the reactions of each material and, using a machine learning model, learns which set of reactions are associated with a specific food or scent (right).Brandon Sánchez-Mejia/UC Berkeley

While the concept of the electronic nose has been around since the 1980s, bringing the technology to life has been tricky. Single gas sensors, like those found in the carbon monoxide detectors in your home, are relatively straightforward to manufacture. But integrating an array of different sensing films onto a single chip is a lot more difficult.

Bassil overcame many of these challenges by using carbon nanotubes as the conducting material, rather than metal oxides. Carbon nanotubes can form layers that are only around a few nanometers thick, which is the same as just a few atoms, or one one hundredth of a human hair. Their large surface area gives them many special qualities, including being highly sensitive at room temperature.

Bassil has created a portable version of the nose that can be controlled with an iPhone app.Brandon Sánchez-Mejia/UC Berkeley

Using a device structure that works at room temperature — rather than needing to be hot — gave Bassil the ability to choose a wider variety of different gas-sensitive...