Smartphones could soon tell your when food has gone off, thanks to a new sensor that costs pence (cents) to produce.
Freshness sensors that can be linked to the devices developed by British scientists can detect gasses from spoiled meat and fish.
The cheap and eco-friendly gadgets will reduce food waste and plastic pollution - and may even bring down prices for shoppers, according to a new study.
Embedded in packaging, they may replace 'best before dates' in meat and fish 'within three years.' They could also be applied to dairy goods and other produce.
Smartphones could soon tell your when food has gone off, thanks to a new sensor that costs pence (cents) to produce. Freshness sensors that can be linked to the devices developed by British scientists can detect gasses from spoiled meat and fish
Study lead author Dr Firat Guder, of the department of bioengineering at Imperial College London, said: 'Although they are 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.'
One in three UK consumers throw away food solely because it reaches the use-by date.
But 60 per cent, or 4.2 million tonnes, of the £12.5 billion-worth ($15.9 bn) of produce we discard annually is safe to eat.
Dr Guder said: 'Citizens want to be confident their food is safe to eat, and to avoid throwing food away unnecessarily because they aren't able to judge its safety.'
The prototypes cost less than two pence each to make. Known as paper-based electrical gas sensors (PEGS), they detect tell-tale gases.
These include ammonia and trimethylamine that signal when meat and fish is no longer fit for human consumption.
The data is read by people simply holding a smartphone up to the packaging.
Dr Guder said: 'These sensors are cheap enough that we hope supermarkets could use them within three years.'
The cheap and eco-friendly gadgets will reduce food waste and plastic pollution - and may even bring down prices for shoppers, according to a new study
The sensors were created by printing carbon electrodes onto readily available cellulose paper.
The biodegradable materials are non toxic, so they don't harm the environment and are safe to use in food packaging.
They are also fitted with 'near field communication' (NFC) tags – a series of microchips that can be picked up by nearby mobile devices.
During laboratory testing on packaged fish and chicken, PEGS picked up trace amounts of spoilage gases quickly and more accurately than existing alternatives, at a fraction of the price.
They could also eventually replace the 'use-by' date – a less reliable indicator of freshness and edibility.
Lower costs for retailers may also eventually make food cheaper for shoppers, say the researchers.
Dr Guder pointed out that PEGS are the first ever commercially-viable food freshness sensors.
He said: ' Our vision is to use PEGS in food packaging to reduce unnecessary food waste and the resulting plastic pollution.'
The study found that consumers rely on use-by dates or even 'sniff tests' to see if their food is safe to eat.
But there is currently no commercially viable, reliable alternative to these options that provides objective feedback on food freshness and safety.
Although developed by food technologists over many years to ensure safety, use-by dates don't take storage and processing conditions of specific items into account.
This can lead to safe and edible food being thrown away by shops and consumers. In addition, most of the food wasted is packaged