Food package changes colour from purple to yellow-green when meat spoils

A packet of meat can look fresh on the supermarket shelf even while bacteria are already multiplying inside. By the time a spoiled smell, discolouration or slimy texture becomes obvious, indicating that the meat has gone stale, the food may no longer be safe to eat.To find a solution to this, researchers at Kyushu University in Japan are working on a packaging material that could give consumers an earlier warning. Their new “smart” hydrogel film changes colour as meat begins to spoil, shifting from purple-red to yellow-green. The flexible material can also repair small cuts in its surface, potentially helping prevent bacteria from entering through damage caused during transport or handling.