Canned food is a convenient food for storing and carrying. But the open canned can not be stored again. The canned fruit contains a large amount of sugar and organic acids. After opening, it is invaded by lactic acid bacteria and yeast in the air. Sugar and organic acids are decomposed into lactic acid, acetic acid, ethanol and other substances, thus making the syrup cloudy, and the fruit has the taste of acid and alcohol. At the same time, under the action of oxygen, it will also discolourate sugar and fruits. Therefore, when canned fruits are opened, they should be eaten at a time and must not be stored again.