It 's easy to tell when your milk has gone bad , the smell , the curdle , the date on top of the bottle .
牛奶的气味，凝结状态和瓶口上标注的日期可以很容易地告诉你牛奶是否变坏了。
It can be hard to finish a whole gallon of milk before it expires , but don 't wait for it to curdle . Instead , set some aside and make cottage cheese .
