食物坏了，不能吃了
最简单常用的表达是
It‘s gone off.
If food or drink goes off, it is not good to eat or drink any more because it is too old.
(食物、饮料等)变质，变坏，腐败
例：
This bacon smells a bit funny - do you think it‘s gone off?
这熏猪肉闻起来有点怪怪的——你觉得它是不是变质了?
It‘s spoilt.
spoil v. /spɔɪl/
When food spoils or is spoiled, it is no longer good enough to eat.
(使)(食物)变质，(使)变坏
例：
The dessert will spoil if you don‘t keep it in the fridge.
如果你不把甜点放在冰箱里，它会坏掉的。
如果你实在想不出别的单词，
脑子里只有bad的话
也是可以表达的
只不过不能用be动词
而应该用
go bad
但其实食物变坏，
也细分很多种
比如说“腐烂”就可以用到
rot
rot
v. /rɒt/
to (cause something to) decay
(使)腐败;(使)腐烂;(使)腐朽
例：
The fruit had been left to rot on the trees.
水果无人采摘，烂在了树上。
Rain has got in and rotted (away) the woodwork.
雨水漏了进来，使屋中的木建部分都朽烂了。
the smell of rotting fruit
烂水果的味道
由于成分不同，
不同的食物变质也会产生不同的化学反应，
比如粥会变馊。
“变馊”用英语怎么说呢?
turn sour
sour可以形容食物腐烂泛酸味，变馊了
sour
v. /saʊər/
to become sour or to make something become sour
(使)变酸;(使)酸腐
例：
Hot weather sours milk.
热天会让牛奶变酸。
Milk sours in hot weather.
牛奶在热天会变酸。
高温和湿气会给细菌滋生提供了生存环境，
食物容易发霉长毛
那食物“发霉”的英文表达是什么?
go mouldy
发霉
mouldy
adj. /ˈməʊl.di/
covered with mould
发霉的
例：
mouldy bread/cheese
发霉的面包/奶酪
These biscuits have gone mouldy,so I will buy some food in the grocery store.
这些饼干发霉了，所以我会去杂货店买点食物。
还有一种情况我们通常就不再吃这个食物了，
那就是它过了它的保质期
"It‘s past its Use-by date."
保质期
use-by date
best-before date
expiration date
这个三个表达之间的区别
Expiration datestell consumers the last day a product is safe to consume. Best before dateon the other hand tells you that the food is no longer in its perfect shape from that date. It may just lose its freshness, taste, aroma or nutrients. It does not necessarily mean that the food is no longer safe to eat. Best before date is basically a quality indicator. Another term that gets mixed up with this is the use by datewhich applies only to perishable goods such as fresh fish or meat. Dispose them off immediately once they have passed the use by date.
Expiration dates告诉消费者产品可以安全食用的最后一天。Best before date告诉你食物从那个日期起就不再处于最佳食用期了。它可能会失去它的新鲜，味道，香气或营养。这并不一定意味着食物不再安全。Best before date基本上是一个质量指标。另一个与此混在一起的术语是use by date，它只适用于像新鲜的鱼或肉这样的易腐货物。一旦过了use by date，需要立即将它们处理掉。