Spoilage detection sensor developed by MIT engineers has presented an innovative answer to a long-standing problem of spoilage detection in packaged foods. Detection of spoilage in foods is the major challenge for any food processor. Rather it might is easier to detect spoilage of foods when it’s not packed. But for the detection of signs of spoilage in products inside the package is still very challenging. In most cases, we have to open the packets showing any suspect of spoilage to predict the whole lot. This method is not efficient as we cannot know about each packet individually.
To come out of this challenge, engineers of MIT have designed a Velcro-like food sensor that is made up of an array of silk micro-needles. These micro-needles can easily pierce into the plastic packaging material to reach sample food for the detection of any signs of spoilage and bacterial contamination.
Velcro-like microneedle food sensor
Each microneedle of the spoilage detection sensor measures about 1.6mm long and 600 microns wide contains a solution of edible proteins found in silk cocoons. These needles are designed by the MIT engineers in a way to draw fluid from the sample food into the back of the sensors when it gets pierced into the sample food. Along with the protein the needle also contains two types of bioink polymers. One of the polymers is sensitive to a molecule in E.coli while the other is sensitive to the change in pH level.
When the fluid from the food comes into contact with these bioinks, a change in color is noticed. One ink changes its color due to the presence of contaminating bacteria E.coli or any other pathogens while the other changes its color if the fluid has a different pH than the predetermined level.
A deeper dive into the sensor
Spoilage Detection Sensor developed by MIT engineers is made from a solution of silk fibroin, a protein extracted from the moth cocoons. The silk fibroin solution is poured into the silicon microneedle mold to give it the shape of needles measuring about 1.6mm long and 600 microns wide after drying which can easily penetrate the food tissues.
After making microneedles, scientists developed solutions for making two different kinds of bio-inks. They mixed color-changing printable polymers with other sensing ingredients. Into one of the bioinks, they added an antibody that is sensitive to the molecules in E.coli. When the bioink comes in contact with E.coli, the antibody will change its shape which in turn changes the way the bioink absorbs light, and hence, the change in color can be detected.
The second bioink they made is sensitive to the change in pH levels that is associated with spoilage. They printed both the bioinks on the surface of the microneedle array in the pattern of letters. Bacteria sensing bioink is printed in the pattern of the letter “E”, next to which pH-sensitive bioink is printed in the pattern of the letter “C”. Initially, both the letters appear blue which changes into the red after sensing spoilage.
Scientists made pores within each of the microneedles to enable them the ability to draw fluid from food material via capillary action. These fluids then reach the bioinks and after few hours the change in color from blue to red can be observed in the letter “E” if food has bacterial contamination and in the letter “C” if there is any change in pH level.
Need for this technology in future
Generally, we assess the spoilage in foods by only judging its surface condition. If the surface is fine then we accept the food but if not satisfactory then we discard the food. This is exactly what the spoilage detection sensor developed by MIT engineers does. This kind of practice makes the improper labeling of the product and hence, we are throwing the food away without knowing that food is spoiled or not.
The surfaces of the food materials are also not smooth and even. There are lots of holes and cavities present over the surface of the food. There might be the possibility that pathogens are embedded into those cavity and surface sensors cannot be able to detect them which will produce biased results. But this new piercing technique improves this kind of limitation and gives us the most accurate analysis. And also, for analyzing the food we don’t have to open the package if the food is in packed form.
The sensor is also made from silk which can easily penetrate through a large spectrum of tissue types, like meat, peaches, and lettuce. Silk also ensures the safety of food after quality analysis as it is completely edible, non-toxic, and can also be used as a food ingredient.
Read more about Active packaging material by extrusion technology
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B.Tech student at National Institute of Food Technology Entrepreneurship and Management