How can you be sure packaged foods that look fresh really are? Japanese researchers have developed a plant-based biodegradable film that changes color as packaged foods, including meats, develop bacterial changes indicating spoilage without opening the package. The research, published in the Chemical Engineering Journal, suggests changes in the color of packaging film occur before any visible spoilage. The material can also repair cuts to itself, keeping out bacteria during shipping and handling. Authors discovered that, in addition to signaling food spoilage, the protective film also extends the shelf life of certain meats by up to twelve hours. Next may be a smart phone app that gives shoppers a reliable and practical monitor of meat freshness.