Many people rely on the sniff test to decide whether food is still safe to eat.
If milk smells fine or leftovers don’t seem off, we often assume they are okay. But the human nose isn’t always reliable.
Every year, millions of people in the United States become sick from food-borne germs that can grow in spoiled or improperly cooked food.
Now, researchers at the University of California, Berkeley, have developed an electronic “nose” that can detect spoiled food much more accurately than people can.
The new device can also identify common food allergens, such as peanuts and walnuts, which can be life-threatening for people with allergies.
The study describing the technology was published in the journal Science Advances.
The electronic nose was developed by Carla Bassil, a doctoral student in electrical engineering and computer sciences at UC Berkeley.
Bassil believes the technology could one day be built into smart refrigerators. Imagine opening an app on your phone and receiving a message that says your broccoli is about to spoil or that your chicken should be eaten today.
Such warnings could help people avoid food waste and reduce the risk of food poisoning.
The artificial nose contains an array of 16 tiny gas sensors. Each sensor reacts to a slightly different mixture of gases released by foods. Together, they work somewhat like digital taste buds.
When food gives off gases, chemical reactions occur on the surfaces of the sensors. These reactions are converted into electrical signals that create a unique “fingerprint” for each smell.
To teach the device how to recognize different foods, Bassil used machine learning, a form of artificial intelligence that learns patterns from data. She trained the system to identify seven foods, including strawberries, blueberries, bananas, walnuts, hazelnuts, cashews and peanuts.
The researchers also taught the electronic nose to distinguish between fresh and spoiled chicken, milk and eggs. Samples were tested when fresh and again after being left at room temperature for one and two days.
The device proved to be remarkably sensitive. It was able to detect as little as 0.05 grams of walnut, which is only about one hundredth of an average shelled walnut. This level of sensitivity could make it useful for detecting allergens that might otherwise go unnoticed.
However, more testing is needed. Researchers have not yet studied how well the device works in more complex environments, such as identifying walnuts hidden inside a cake or detecting spoiled food in a refrigerator filled with many different items.
The idea of an electronic nose is not new. Scientists have been exploring the concept since the 1980s. The challenge has been fitting many different types of sensors onto a single chip.
Bassil overcame this problem by using carbon nanotubes, extremely thin materials that are only a few atoms thick. These nanotubes are highly sensitive at room temperature and allowed the team to use a wider range of sensing materials in a simpler manufacturing process.
The researchers have already created a portable version of the electronic nose that can be controlled using an iPhone app. Future studies will focus on improving the device’s sensitivity and testing it in real-world settings.
One day, this tiny electronic nose may help keep our food fresher, reduce waste and protect people from dangerous food allergies.
