2022-05-05

鸡蛋的吃法有很多，水煮蛋是最常见的一种。水煮蛋烹饪简单，便于食用，高蛋白低热量，是一种健康营养的美味。细心的人可能会发现，煮鸡蛋的蛋黄表面有时会呈灰绿色。这是什么原因？这样的鸡蛋还能吃吗？

Some hard-boiled eggs have a gray or green ring of discoloration between the white and the yolk1, which might prompt you to wonder if the chicken in question had some exotic disease or whether the egg is safe to consume.

一些煮老了的鸡蛋蛋黄和蛋白相接触的一层表面会成灰色或绿色，有人可能会因此怀疑母鸡得病了，或者鸡蛋是否可以安全食用。

Good news: It is. The gray coloring appears due to a chemical reaction when boiling the egg. Proteins in the egg are held together by sulfur2, which breaks down in heat and becomes hydrogen sulfide. Iron in the egg yolk can alter it further so it becomes ferrous (iron) sulfide on the surface. Too much iron in your water can produce a similar result.

好消息：可以吃。煮鸡蛋时，蛋黄表面由于化学反应而呈现灰色。鸡蛋的蛋白质中含有硫元素，高温下蛋白质分解形成硫化氢。蛋黄中的铁元素会进一步与之发生反应，使其表面形成硫化亚铁。水中含铁过多也会导致类似的结果。

What does this have to do with the color? It's the iron sulfide that creates the gray (or green) rings around the egg, and that's usually a result of overcooking it.