Engineers at MIT have developed a Velcro-like sensor that can detect if food is contaminated or spoiled.
Microneedles attached to the sensor pierce through packaging to sample food for signs of E.coli and other pathogens.
Molded from edible proteins found in silk cocoons, the microneedles draw fluid into the sensor, which has letters printed with color-changing ‘bioink’ to detect impurities.
One ink is designed to go from blue to red if it comes into contact with bacteria like E. coli and the other is pH-sensitive that only changes if the food is spoiled.
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Sensors developed at MIT changed from blue to red in the presence of E.coli and spoilage in store-bought fish. One kind of bioink in the sensors is sensitive to the presence of bacteria, while another detects changes in pH
Researchers attached the sensor to pieces of raw fish that had been injected with E. coli.
The ink that detected bacteria was used to make an ‘E,’ while the ink that measured pH levels made a ‘C.’
After less than a day, the ‘E’ turned from blue to red in all the samples, indicating the fish was contaminated with E.coli.
After a few hours, the pH-sensitive ‘C’ also changed hue, signaling the filet had also spoiled.
Microneedles made from silk can puncture plastic wrap to test if meat, fish and other products are contaminated or spoiled. Silk is nontoxic and can be used as a food ingredient
Their work, published today in Advanced Functional Materials, could lead to smart food sensors that head off outbreaks but also prevent consumers from throwing out food that is still safe to eat.
Americans throw out nearly 40 million tons of food every year, much of which is still perfectly edible.
‘There is a lot of food that’s wasted due to lack of proper labeling, and we’re throwing food away without even knowing if it’s spoiled or not,’ said co-author Benedetto Marelli, a professor in MIT’s Department of Civil and Environmental Engineering.
An illustration shows a proposed food quality monitoring system that uses silk microneedle with printed bioinks as colorimetric sensors. The technology could be used every step of the way, from the processing plant to the kitchen counter
‘People also waste a lot of food after outbreaks, because they’re not sure if the food is actually contaminated or not,’ he added. ‘A technology like this would give confidence to the end user to not waste food.’
Having developed a silk-based microneedle that penetrates and delivers nutrients to plants, Marelli collaborated with A. John Hart, a professor of mechanical engineering who devised a high-resolution printing technique.
‘Assessing the health of food by just measuring its surface is often not good enough,’ said Hart.
‘At some point, Benedetto mentioned his group’s microneedle work with plants, and we realized that we could combine our expertise to make a more effective sensor.’
The team wanted to create a sensor that could puncture the surface of many types of food and realized silk microneedles were the perfect conduit.
‘Silk is completely edible, nontoxic and can be used as a food ingredient,’ Marelli said.
‘And it’s mechanically robust enough to penetrate through a large spectrum of tissue types – like meat, peaches, and lettuce.’
The bioink used in the test contained antibodies sensitive to E. coli, but it could be adapted to identify other bacteria.
A recent outbreak of salmonella that infected dozens of people across 12 states was traced to tainted peaches.
The sensors indicate contamination and spoilage faster than existing technology, which only detects pathogens on food surfaces.
The silk microneedle arrays seen here could head off outbreaks but also prevent consumers from throwing out food that is still safe to eat. Americans throw out nearly 40 million tons of food every year, much of which is still perfectly edible
‘There are many cavities and holes in food where pathogens are embedded, and surface sensors cannot detect these,’ said Doyoon Kim, an environmental engineer at MIT who worked on the project.
‘So we have to plug in a bit deeper to improve the reliability of the detection. Using this piercing technique, we also don’t have to open a package to inspect food quality.’
The team is still refining the technique but envisions it being used at every stage of food production, from the processing plant to the kitchen counter.
WHAT TIPS CAN BE FOLLOWED TO AVOID FOOD POISONING?
1. Keep a clean work space
Germs can survive across all of the different surfaces in the kitchen, so it’s essential to keep the cooking area and your hands clean.
2. Avoid cross-contamination
Raw meat, poultry, seafood and eggs can spread germs to ready-to-eat foods if not kept separate.
The CDC recommends using separate cutting boards and plates when handling these ingredients.
They should also be stored separately in the fridge.
3. Use a thermometer
To cook food safely, the internal temperature must get high enough to kill the germs that could cause food poisoning.
The correct internal temperature varies by ingredient, and only surefire way to tell if food is safely cooked is to use a food thermometer.
4. Store food properly
Storing food properly is essential to combating harmful bacteria.
Perishable food should be refrigerated within two hours of when it was purchased, and the refrigerator should be set to below 40°F.
5. Don’t rely solely on expiration dates
Expiration dates aren’t the only indication of when a food item should be thrown away.
If something seems to have a strange smell or color, it’s probably better to be safe and pitch it.
6. Don’t thaw frozen food on the counter
Thawing frozen foods on the counter allows bacteria to multiply quickly in the outer parts as they reach room temperature.
Frozen foods should be thawed in the refrigerator, in cold water, or in the microwave.