This article was originally published on MSN.com on March 13, 2013. It was written by Michelle V. Rafter. View the original article here.

What if you could tell how fresh a half-gallon of milk was or how long a pound of salmon would keep — not from the “sell by” date on the packaging, but from the food itself?

University researchers in Europe think they’ve developed a sensor that could do just that, and it could be ready for grocery shelves as soon as five years from now.

Sensors are the latest salvo in the battle against food waste, which has become rampant. Every year, U.S. households throw away an estimated 40% of their food, equal to $2,275 a year for a family of four.

Much of that waste comes from confusion over food expiration dates and inefficient food practices at home, in restaurants and in the food industry supply chain, says Dana Gunders, a food and agriculture scientist with the Natural Resources Defense Council, a national environmental advocacy group.

Electronic sensor circuits already exist that could detect freshness by measuring conditions like acidity levels. But existing sensors use electronics made from silicon, which makes them too costly to incorporate into food packaging. A new generation of sensors contains electronics made from plastic, and they could be made for just over a penny apiece, according to a report published last month by researchers at Eindhoven University of Technology in the Netherlands. That makes sensors cheap enough to add to a bag of potato chips, for example, or to the plastic wrap used to package fresh meat, fish and produce.

Consumers who are conscientious about checking expiration dates say they are unsure about sensors. A sensor would be “cool, but I wouldn’t trust it until it was on the market for a very long time and was proven accurate,” says Beverly Blair Harzog, a credit card expert and consumer advocate in Johns Creek, Ga.

“I’m a geek, but would never use an app,” says Ron Doyle, a Denver Web developer. “An expiration date needs to be permanently attached to the product. But I also trust my own senses more than printed numbers — and routinely buy discount items that are near expiration.”

It’s actually smart to give food the sniff test, Gunders says. “We have a very strong instinctive behavior about food, we wouldn’t eat it if by smelling it or tasting it” we could tell it was bad, she says.

Tech advances spare wasted food

While plastic sensors may be a long way off, other new technologies already are helping combat food waste. Some restaurants are putting spoiled produce or other food on scales that are hooked up to software to track waste. The LeanPath System could help eateries discover what products it’s tossing week-in and week-out. If, for example, broccoli is routinely going to waste, chefs could stop ordering as much or put more cream of broccoli soup on the menu, Gunders says.

Further up the supply chain, some pallets used for shipping food from the farmer, manufacturer or distributor to grocery stores now have built-in sensors that track data on how hot or cold items have gotten on route, as well as which pallets were loaded first, all the better to help grocers know which items to unload first, Gunders says. 

Grocery stores are also doing their part, implementing zero-waste practices, including donating food that’s still edible to food banks and similar groups, or giving it to farms to use as feed “and at the very minimum, diverting the organics from the waste stream to be composted,” according to Peter Cooke, a program manager at the Manomet Center for Conservation Sciences, a Massachusetts environmental advocacy group.

Coupled with advances that make kitchen appliances smarter, the day could come when refrigerators recommend recipes based what food is stored inside or communicate with grocery shoppers via a smartphone app so they could know which items they already have at home, Gunders says.

Steps to wasting less food

Until then, though, here’s what experts say shoppers can do to eliminate food waste:

Don’t toss out food on the expiration date. Manufacturers use sell-by or expiration dates to guarantee that the food still has a shelf life after that date, according to Gunders. The fact that 60% of consumers throw away food on the sell-by date “shows how much people don’t understand those dates and are throwing away good food,” Gunders says.

Craft realistic weekly shopping lists. People tend to grocery shop once a week for what they think they’ll need for the next seven days, but it’s often too much, which can lead to waste. “Be mindful” of what you’re buying, she says.

Freeze food before it goes bad. “Freezers are our friends,” Gunders says. It’s possible to freeze all kinds of food, from milk and bread to beans and herbs.

Monitor food portions. “We have had a huge increase in portion sizes in the last 40 years in the United States, and it’s increased our waistlines and our food waste,” Gunders says. Consider sharing restaurant meals; many establishments let diners split their orders. Or bring home what you can’t finish. “We’re on a mission to change get people to change calling them ‘doggy bags’ for ‘goody bags,'” she says.

Use an app. Gunders recommends smartphone apps such as Still Tasty or Shelf Life that share data on the shelf life of many food and beverages, and include alarms that can be set to go off when certain items should to thrown out.

Follow grocery stories on social media. More of them are using social marketing techniques to help customers reduce their food waste at home, Cooke says.