Low-cost, printable, smartphone-linked sensors could be a better indicator than labels of when food has passed its use-by date, say UK researchers. But there is a flaw in their thinking. Chris Middleton reports.

Food waste has hit the headlines recently, with debates raging about the amount of food being thrown in the bin, while the needless packaging of fruit and vegetables contributes to soaring plastics pollution.

According to anti-waste charity WRAP (the Waste and Resources Action Programme), one-third of all food produced in the world is lost or wasted. WRAP estimates that, in 2015, UK household, hospitality, manufacture, wholesale, and retail food waste amounted to 10 million tonnes, 70 percent of which was intended for consumption (the remaining 30 percent being inedible parts, such as bones).

In other words, seven million tonnes of actual food – worth roughly $20 billion – are being dumped every year in the UK alone. Annually, the average British family throws away £810 worth of food, says WRAP.

‘Best Before’ dates are often to blame; these are about perceived quality rather than food safety, according to the Food Standards Agency. The ‘Use By’ date is the key measure of whether food is safe for consumption, says the FSA, and one-third of UK consumers throw food away when it reaches this date, even if it passes the ‘smell test’.

This is in accordance with FSA advice – which is also endorsed by anti-food-waste organisations, such as Love Food Hate Waste, a division of WRAP.

However, according to Imperial College London, up to 60 percent of food that has reached its use-by date may still be safe to eat. But how can consumers or retailers tell, if the smell test is not a reliable guide?

Low-cost sensors may be the answer, according to Imperial. Researchers at the university’s Department of Bioengineering, led by faculty member Dr Firat Güder, have developed prototype smartphone-linked sensors for meat and fish, which they hope will be adopted by supermarkets.

The paper-based electrical gas sensors (PEGS) consist of carbon electrodes printed on cellulose paper, which detect trace spoilage gases, such as ammonia and trimethylamine, in meat and fish products. The PEGS’ construction materials are biodegradable and nontoxic, so don’t harm the environment and are safe to use in food packaging.

The devices can be produced for as little as two cents apiece and could have further applications, such as detecting chemicals in agriculture, air quality monitoring, and detecting disease markers in breath.

The team hopes the new sensors will eventually replace use-by dates, help reduce food waste, and lower costs by minimising retail losses. Dr Güder said: “Citizens want to be confident that their food is safe to eat, and to avoid throwing food away unnecessarily because they aren’t able to judge its safety.

“These sensors are cheap enough that we hope supermarkets could use them within three years. Our vision is to use PEGS in food packaging to reduce unnecessary food waste and the resulting plastic pollution.”

First author of the study, Imperial researcher Giandrin Barandun, added: “Although the food industry – and consumers – are understandably cautious about shelf life, it’s time to embrace technology that could more accurately detect food edibility and reduce food waste and plastic pollution.”

A commendable aim and promising research, but is it really that simple? In order for consumers to be able to access the sensor data from their smartphones – either on supermarket shelves or in their refrigerators at home – the PEGS have to be combined with near-field communication (NFC) tags. These may be the weak link in the concept by themselves contributing to waste and environmental damage.

Many NFC tags contain materials that are either not biodegradable or are produced using high-energy refinement processes. Those designed to have a minimal impact on the environment are more expensive to produce – roughly 15 cents a unit – while those that are not are expensive to sort when (or if) the packaging is recycled.

On low-margin food, an additional cost of 17 cents a unit on each package is unlikely to represent a viable solution to retailers – some of whom achieve higher margins by packaging up small quantities of goods. So while the innovation (which was funded by the Engineering and Physical Sciences Research Council) may help to reduce food waste, it may create new problems and environmental challenges.

One option is to not go for a smartphone- and NFC-based solution, but instead opt for smart labels that use the same PEGS technology. However, Dr Güder admits that consumers are often put off by labels that indicate that, while the food may still be edible, it may not be at its best.

So, while PEGS are a promising innovation with multiple applications, until the problem is solved of making their data human- and/or device-readable without creating new sustainability problems, they are no off-the-peg solution.