Why use-by labels have passed their expiration date

Imperial College London researchers have created spoilage sensors that are cheap and environmentally friendly.

19 June 2019
food wastehealthplasticpackagingsupermarketstechnology
image credit: Getty Images

Use-by dates may have outlived their usefulness, as advances in tech are producing more efficient means of assessing freshness.

Scientists from Imperial College London have developed prototype sensors that are biodegradable, cheap to make and use cell phone technology. They work on packaged meat and fish, allowing both retailers and consumers to determine whether food is safe to eat via a mobile device.

The researchers say the new sensors could help detect spoilage and reduce food waste, as well as being a more reliable alternative to use by dates – and could be in supermarkets within three years.

The new sensors cost 2 US cents to make and are known as paper-based electrical gas sensors (PEGS), because they detect spoilage gases like ammonia and trimethylamine in meat and fish products.

One in three UK consumers throws away food solely because it reaches the use-by date, but 60% (or 4.2m tonnes) of the £12.5bn worth of food thrown away each year is safe to eat.

Everybody wins

Apart from consigning use-by dates to the past, sensors could also lower costs for both retailers and consumers. Supermarkets could use targeted pricing based on the data, discounting stock that is turning but still safe to eat and selling the freshest products at full price, according to the researchers.

Dr Firat Güder, who led the research, said that for the tech to be successful it was important that it benefitted every part of the chain, from packaging manufacturers to retailers and consumers.

“Although they’re designed to keep us safe, use-by dates can lead to edible food being thrown away. In fact, use-by dates are not completely reliable in terms of safety as people often get sick from foodborne diseases due to poor storage, even when an item is within its use-by,” he 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. Our vision is to use PEGS in food packaging to reduce unnecessary food waste and the resulting plastic pollution.”

A more sensitive system

During lab testing on packaged fish and chicken, PEGS picked up trace amounts of spoilage gases quickly and more accurately than existing sensors, according to Imperial College London.

Existing food spoilage sensors are either too expensive for common use – often comprising a quarter of overall packaging costs – or are too difficult to interpret, claimed the researchers. Some types, like colour-changing sensors, could increase food waste as consumers might interpret even the slightest colour change as bad food.

Naturally, Imperial College London claimed its prototype was superior on several fronts: it functions effectively at nearly 100% humidity while most sensors struggle above 90%; it works at room temperature and does not need to be heated, consuming very low amounts of energy; and the sensors are sensitive only to the gases involved in food spoilage, whereas other sensors can be triggered by non-spoilage gases.

Packaging partners and capturing more food

Made using ballpoint pens, robotic cutters and cellulose paper, the sensors incorporate near-field communication (NFC) tags, meaning their data can be read by any mobile device close by (providing the phone has NFC capability).

“We believe our very simple technique could easily be scaled up to produce PEGS on a mass scale by using existing high-volume printing methods such as screen printing and roll-to-roll printing,” Dr Guder commented.

Currently, the team are developing an array of PEGS in which each sensor detects a different chemical. Using this technique would allow for unique signals for different gases and/or changing humidity, which would make the technology applicable to a wider variety of food types.

They have also launched a start-up company called Blakbear and partnered with a packaging manufacturer to help bring the technology to market.

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