I thought this was so clever: a simple way to tell if food has gone off, without having to guess, sniff, or rely on a (frequently unreliable) sell-by date.

Developed by researchers in London, paper-based electrical gas sensors (“PEGS”) can detect spoilage gases like ammonia and trimethylamine in packaged fish and chicken.

Smartphones can read the data, so you simply hold your phone up to the packaging to learn whether a food is safe to eat.

In lab tests, PEGS identified trace amounts of spoilage gases more accurately than existing sensors.  And since they’re much cheaper to manufacture, the hope is that once PEGS are widely used, the savings for retailers might get passed along to the rest of us as lower food costs.

No More ‘Sniff Tests’: Cheap Biodegradable Sensors Can Tell Smartphones When Food Has Gone Bad