A chip to weed out the bad apples

A simple sensor could take the guesswork out of determining when food is spoiled, cutting wastage and saving retailers huge sums of money.

One-third of food produced worldwide never makes it to the plate. The UK alone disposes of nearly 9 million tonnes of food annually, including a quarter of all the food that households purchase – at a cost of £10 billion to the nation.

Spoilage is part of the problem, but determining when food is no longer good is often a guessing game. Now, chemists at the Massachusetts Institute of Technology (MIT) have developed a sensor that monitors the ripening of produce. Each sensor, no bigger than a computer chip, is composed of thousands of carbon nanotubes designed to respond to the presence of ethylene, a chemical released as produce matures. The sensors could be attached to boxes of fruit and vegetables, according to lead scientist Timothy Swager, and scanned with a handheld device to assess their ripeness. This would inform retailers of pending spoilage, signalling when it’s time to place items on sale – and thereby cut losses by up to 30%, Swager claims.

While ethylene monitoring is commonplace, existing systems are pricey, often costing well over US$1,000 for a single unit. But rising demand and increased production have led to a precipitous drop in the price of carbon nanotubes, bringing the cost of the new sensors down to just 25 cents each. This could make it viable to track the ripening of produce for an entire warehouse or shipping container.

To streamline the process, the MIT team is also investigating radio frequency identification (RFID) tags that track sensors with the wave of a handheld device. “With RFID, you can quickly check the ripeness of all your fruit wirelessly”, says Jan Schnorr, a chemist involved with the project.

Nanotechnology stands to enhance food packaging in numerous ways: extending shelf life, alerting retailers to pathogens, and even eliminating harmful bacteria. But the health effects of nanotechnology are not fully understood, and regulators are examining possible risks, such as skin and respiratory conditions. Andrew Wadge, Chief Scientist at the Food Standards Agency (FSA) has said that although nanotechnology does not have a large presence in the food retail market, the FSA “fully expect that to change”.

Schnorr says the MIT invention has elicited “an overwhelming response from companies in the food and sensing sectors”, but that it’s premature to name investors. The team has patented the sensors and plans to market them next year. – Katherine Rowland

Photo: Dr. Katherine Mirica