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John Oliver would probably approve of this 3D-printed milk cap that detects spoilage

On the latest episode of Last Week Tonight, John Oliver bemoaned a major U.S. problem: food waste. Using a clip from Good Morning America, he made that point that sell-by dates are often misleading. In the video, it’s revealed that three separate cartons of the same brand of 2 percent milk at the same grocery store in the same dairy case have three different dates: A “best-by date,” a “sell-by date,” and a date with no other identifying information. Clearly, there’s only one way for us to tell if our milk has gone bad: by sniffing it.

But engineers from UC Berkeley and Taiwan’s National Chiao Tung University want to change that with a 3D-printed cap that determines when milk goes bad. When bacteria starts to multiply, the 3D-printed plastic embedded with circuitry and sensors detects changes in the electrical signals when you tip the container over and slosh milk on the cap, according to the results published in the journal Microsystems & Nanoengineering. The system could also work for juice, according to the abstract.

Related: LED indoor farms could change the food industry, and help solve world hunger

“This 3D-printing technology could eventually make electronic circuits cheap enough to be added to packaging to provide food safety alerts for consumers,” senior author Liwei Lin, a mechanical engineering professor and co-director of the Berkeley Sensor and Actuator Center, told Berkley News.

MIT researchers published their findings on an RFID tag that would detect spoiled food last year, and an Indiegogo campaign was launched for a Foodsniffer device that could also tell when meat was going bad.

Americans throw away about $165 billion worth of food each year, according to the Natural Resources Defense Council, and any technology that detects when something is still safe to eat could help reduce all that waste. Despite the arbitrariness of expiration dates, it would still be nice to have evidence of edibleness beyond the sniff test.