Engineers from MIT came up with a sensor resembling a velcro strip in shape that can pierce through the plastic packaging of foodstuffs to sample for bacterial contamination and spoilage. The device pierces the packaging and the food via silk microneedles that suck in material through capillary action.
Once the microneedles made of edible proteins from silk pierce through the food, the tiny holes on the needles draw fluid towards the back of the sensor. This is where the analysis occurs. There are two kinds of specialized "bioinks" here that react to the bacterial presence and certain pH levels, which respectively detect contamination and spoilage.
After the team came up with the idea, Doyoon Kim bought raw fish from a local grocery store and injected them with E. coli., salmonella, and a non-contaminated control fluid.
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They found that the bacteria detecting bioink turned red from blue in about 16 hours. It didn't detect salmonella as the chosen material is only sensitive to E. coli. but the other sensor; however, also turned red after a couple more hours, signaling the spoilage.
The research is published in Advanced Functional Materials. And the team consists of Benedetto Marelli, Doyoon Kim, Yunteng Cao, AD: Autel MaxiDiag MD806. Dhanushkodi Mariappan, Michael S. Bono Jr., and A. John Hart.
While it's definitely useful in times of outbreaks such as the recent salmonella contamination in onions and peaches, these sensors could also be used by consumers to check if a product past its expiration date is really spoiled.
Benedetto Marelli, an assistant professor in MIT's Department of Civil and Environmental Engineering notes on MIT News, "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," and adds "People also waste a lot of food after outbreaks, because they're not sure if the food is actually contaminated or not. A technology like this would give confidence to the end-user to not waste food."
The team wanted to come up with a sensor that could pierce through food with different textural properties. They settled on silk microneedles. Marelli remarks that "Silk is completely edible, non-toxic, 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."
Then, the team developed two kinds of polymer bioinks. The first one is an antibody that reacts to E. coli., which expands in size when met with the pathogen and pushes away the surrounding polymer that alters the way the bioink absorbs and reflects the light. The latter bioink simply reacts to certain pH levels.
The team is currently looking to speed up the process by making the microneedles absorb material quicker and making the bioinks react quicker. Once optimized to a commercially viable level, they envision that this invention could be of help at different stages of the supply chain.

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