Foodborne diseases, commonly known as food poisoning, are a very common occurrence. According to the Centre for Disease Control and Prevention (CDC), roughly 48 million people in the USA get sick and about 3000 people die every year due to foodborne diseases. This has led researchers to work on technologies that would let a customer know if food is spoilt or not. The following are three independent research works on such sensors that can detect food spoilage.

Gas detection with chemiresistors

Researchers at the Massachusetts Institute of Technology (MIT) working under Professor Timothy Swager have developed an inexpensive, portable sensor system that can detect the gas emitted by spoilt food.

The device, based on modified carbon nanotubes, can detect amines produced by decaying meat. (Image courtesy: MIT)
The device, based on modified carbon nanotubes, can detect amines produced by decaying meat. (Image courtesy: MIT)
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Modified sensor: The sensors used here are made from modified near-field communication (NFC) tags that can be read by most of the new model smartphones with NFC capability. The electrical circuit in an NFC tag is cut and re-joined by drawing lines with a pencil made of carbon nanotube based compounds called metalloporphyrins. Such modified tags are called as chemically-actuated resonant devices (CARDs). These carbon nanotubes are chemiresistors, which means they change their resistance according to the changes in the surrounding chemical environment. Metalloporphyrins easily bind with amines, a type of compound produced during the decay of meat etc. When this binding occurs the resistance of the carbon nanotube increases, which shifts the radio frequencies at which power is transferred to the device.

Transferring to a smartphone: The magnetic field pulses at radio frequencies emitted by the phone induce a potential to CARDs, and the current through the nanotubes is measured and relayed to the phone. The CARD responds to the smartphone only if it can receive sufficient power at the radio frequencies transmitted by the phone, allowing the phone to determine whether the circuit has been altered and hence detect the decay.

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Optical sensors detect volatile compounds

The CheckPack optical sensor can detect the quality of food inside a container and warn the users when the food is spoilt with the help of volatile biomarkers coated on its surface.

This research started in November 2013 and would run for four years. It is a joint collaboration between Ghent University, VU University and Radboud University, and is funded by IWT, a Flemish government agency for Innovation by Science and Technology.

This scientific research project aims at developing an integrated optical nose system for food packaging. (Image courtesy: CheckPack)
This scientific research project aims at developing an integrated optical nose system for food packaging. (Image courtesy: CheckPack)

Biomarkers for detection: When the volatile components are in contact with the biomarkers, their refractive index changes. This is sensed by the infrared (IR) light directed towards the sensor, and this causes a wavelength shift of the IR light reflected by the sensor. Based on the shift one can determine the volatile components and their concentration inside the container using the reference mathematical model.

MIP for selective detection

Molecularly-imprinted polymers (MIP) are a class of synthetic polymers developed by John Hopkins University Applied Physics Lab (APL) that can detect selective substances. The inexpensive and tiny MIP-based sensor developed by APL has an affinity to bind to amines and changes their colour when binding is achieved. A significant change in colour helps the users understand if the food is spoilt.

Reduced sickness and food wastage

Introduction of such inexpensive, portable devices for identifying spoilt food not only reduces sickness due to food poisoning, but also reduces wastage of food as the customer needs to throw only the food that has spoilt and can confidently use the rest of the food. This provides more accurate information than the expiry date on food packets. All these researches are in the prototype stage, have filed for patents, and are hoping to license them for commercial development.

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The author is a dancer, karaoke aficionado, and a technical correspondent at EFY. Find her on Twitter @AnuBomb.

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