“Most of us are familiar with the practice of checking the use-by dates on food packaging labels. It turns out that many customers throw away the food by those dates, even though in many cases the food is still safe to eat.
Researchers at Imperial College in London hope to change that practice. They have developed paper-based electrical gas sensors, called PEGS, which can detect spoilage gases like ammonia and trimethylamine in meat and fish products—items consumers are particularly leery of using past the use-by date. The prototype sensors cost two U.S. cents to make and can be read by smartphones, enabling users to easily check the packaging to see if the food is still safe to eat…”