在超市购物时，我们都会特别留意一下食物的保质期有多久，是否新鲜，以免买到过期的商品。

“保质期”指产品的最佳食用期，可以翻译为“best-before date，shelf life，expiration date或freshness date”，表示“the length of time that a product, especially food, can be kept in a shop before it becomes too old to be sold or used”。

超出保质期的食品即“过期食品”，可以翻译为“expired food”。

例句：

新鲜水果的保质期很短。

Fresh fruit has a very short shelf life.

但是过期的苏打水跑气，味道也会大打折扣。

But soda past its expiration date goes flat and loses much of its taste.

酸奶已经过期了。

This yogurt is past its sell-by date.