from cbsnews.com: You might not have to smell sour milk for much longer. Chinese scientists have developed “smart tags” that stick to containers and change color when a food has gone bad. The gel-like tabs — which are about the size of a corn kernel — are safe and inexpensive, according to the creators, and could be stuck to cans and bottles to spot spoilage, even before the package is opened. The scientists successfully tested the tags on milk, by exposing it to different temperatures and bacteria until it spoiled. They say tags can be customized to work on canned goods and even medication bottles. “We successfully synchronized, at multiple temperatures, the chemical evolution process in the smart tag with microbial growth processes in the milk,” lead researcher Dr. Chao Zhang, a scientist at Peking University in Beijjing, said in a statement.