Skip to main content
Move the World.
Food Contamination

Lead Image Courtesy of Jose-Luis Olivares / MIT / Doyoon Kim et al.

It doesn't take much to know that some foods are spoiled — a single whiff of rotten milk is enough to let you know you should pour it down the drain.

But some spoiled foods are indistinguishable from their fresh counterparts, and the same goes for foods contaminated by bacteria such as E. coli and Salmonella — you won't know that they aren't safe to eat until you find yourself battling food poisoning hours after consumption.

There's also a flip side to this scenario. People will throw out food because its "best by" or "sell by" date has passed, despite the fact that most of this food is still safe to eat. In fact, a full third of the food produced in the U.S. is wasted due to consumers' confusion over labeling.

"Imagine going to the grocery store and buying three bags of groceries, and as you walk out, you throw one of those bags in the garbage can," Frank Yiannas, a deputy commissioner at the FDA, told NPR in 2019. "It sounds ridiculous, but in essence that's what's happening every day."

There are sensors that can help detect food contamination or spoilage. However, they usually sit on the surface of the food or on the packaging so they can't catch any warning signs lurking below.

Now, researchers from MIT have developed a sensor that pierces food and then changes color in the presence of food contamination or spoilage.

Sensing Food Contamination

MIT's sensor is about the size of a postage stamp and looks like the spiky side of velcro. To create it, the researchers poured a silk protein extracted from moth cocoons into a microneedle mold.

"Silk is completely edible, nontoxic, and can be used as a food ingredient, and it's mechanically robust enough to penetrate through a large spectrum of tissue types, like meat, peaches, and lettuce," researcher Benedetto Marelli told MIT News.

The microneedle patch detects food contamination more quickly than other sensors.

The researchers drilled a hole straight up through each microneedle, creating a direct path from the tip of the spike to the back of the patch.

Next, they created two special bioinks: one that changes color in reaction to E. coli and the other to pH levels that would indicate a food spoilage. They printed the E. coli bioink in the shape of the letter "E" on the back of the microneedle patch. The pH bioink was printed as the letter "C." Both letters were initially colored blue.

Testing the Microneedle Patch

To test their sensor's ability to catch food contamination, the researchers injected filets of raw fish with either E. coli, Salmonella, or a contaminant-free liquid.

About 16 hours later, the "E" changed from blue to red on the fish containing E. coli, indicating that the bacteria had been correctly identified. The sensor on the Salmonella sample remained blue, meaning it was able to discern between the two bacteria.

After 24 hours, the letters on all of the fish samples changed to red, indicating that they'd spoiled.

food contamination

The microneedle patch designed to detect food contamination. Credit: Felice Frankel

This is faster than other sensors designed to detect food contamination and spoilage, according to the researchers. The sensor also has the advantage of being able to monitor food still in packaging — the microneedles can pierce right through it.

Still, the researchers would like to cut down on the amount of time it takes their sensor to sound its warning, so that's what they're working on now. They also plan to test the sensor's ability to catch other bacteria, such as Salmonella, and to work on other types of food, including produce.

Eventually, the sensor could make its way into the hands of food manufacturers — or even members of the public interested in testing questionable food before deciding whether to eat it or toss it in the trash.

We'd love to hear from you! If you have a comment about this article or if you have a tip for a future Freethink story, please email us at [email protected].

Up Next

Dispatches
"Cybersecurity for Plants" Can Stop Germs from Hacking Our Food Supply
Dispatches
"Cybersecurity for Plants" Can Stop Germs from Hacking Our Food Supply
Computer hackers exploit flaws in code to access systems and take what they want; plant diseases work the same way.
By John Herlihy

Computer hackers exploit flaws in code to access systems and take what they want; plant diseases work the same way.

Agriculture
This Massive Farm Robot Is Helping Secure the Future of Food
Farm Robot
Agriculture
This Massive Farm Robot Is Helping Secure the Future of Food
A massive farm robot is analyzing crops in Arizona, helping identify ones that could grow in hotter climates to help secure the future of food.

A massive farm robot is analyzing crops in Arizona, helping identify ones that could grow in hotter climates to help secure the future of food.

Dispatches
Supercharging Photosynthesis Can Grow 40% More Food
Supercharging Photosynthesis Can Grow 40% More Food
Dispatches
Supercharging Photosynthesis Can Grow 40% More Food
We need a lot more calories to feed a growing world, and these scientists may have figured out how to get them.
By Amanda Cavanagh

We need a lot more calories to feed a growing world, and these scientists may have figured out how to get them.

The Student Laboratory Reinventing Food To Stop Waste
The Student Laboratory Reinventing Food To Stop Waste
Watch Now
The Student Laboratory Reinventing Food To Stop Waste
Inside the food laboratory inventing new foods to prevent waste.
Watch Now

As much as 40% of American food goes to waste — and much of that comes from companies. The food lab at Drexel University is helping companies “upcycle” unsold products into new ones and find ways to turn scraps or byproducts into great foods people want to buy. Students work with customers and products to create new ideas and products that the companies can produce with food that would otherwise go to waste. It helps give...

Reducing Food Waste and Feeding the Hungry
Reducing Food Waste and Feeding the Hungry
Watch Now
Reducing Food Waste and Feeding the Hungry
What if instead of throwing out leftover food, we used it to feed the hungry?
Watch Now

Hunger effects nearly 15 million people in the United States, yet we rank number one in the world when it comes to food waste. A non-profit called Rescuing Leftover Cuisine is on a mission to take what would become food waste and use it to feed the hungry. Through their web app, restaurants, hotels, and catering companies can offer excess food for volunteers to pick up and bring to homeless shelters. So far, Rescuing...

Future of Food
These Pioneers are Building the Sustainable Food Systems of Tomorrow
These Pioneers are Building the Sustainable Food Systems of Tomorrow
Future of Food
These Pioneers are Building the Sustainable Food Systems of Tomorrow
In a new Freethink original series, Michael O'Shea goes around the world to introduce us to the scientists who are working hard to ensure that we can feed our future world.

There are currently over 7 billion human beings alive on Earth --- and in 2050 the world's population will rise by almost 2 billion. That's a lot more mouths to feed considering that roughly 11 percent of the world goes hungry today. "in the next 40 years, we need to produce the same amount of food as we did over the last 8,000 years." Ernst van den...

Building Community
“Community Fridges” Are Helping Fight Food Insecurity
Community Fridges
Building Community
“Community Fridges” Are Helping Fight Food Insecurity
Community fridges stocked with donated food that’s free for the taking are helping neighborhoods across the U.S. overcome food insecurity.

Community fridges stocked with donated food that’s free for the taking are helping neighborhoods across the U.S. overcome food insecurity.

Coded
What We Mean When We Talk About Hacking
What We Mean When We Talk About Hacking
Coded
What We Mean When We Talk About Hacking
We've all heard it before: "I was hacked!" But that can mean a lot of things. We take a look at some of the big ones.
By Mike Riggs

We've all heard it before: "I was hacked!" But that can mean a lot of things. We take a look at some of the big ones.