They can mould or ferment rapidly once the container is opened, in the case of aluminum cans, and glass or plastic bottles which have less perfect seals should be viewed as unsafe even before opening.

一旦密闭容器被打开，它们可能会很快地发霉或者发酵，铝罐、玻璃或者塑料罐都可能密封得没有那么好，甚至往往在被打开之前就是不安全的。