Home » Programs » Science Notes » Ring Around the Yolk

Ring Around the Yolk

When you hard boil and slice an egg, you may notice a dark green ring around a yolk. This is iron sulphide which is formed by chemical reactions that take place if an egg is heated for a long time.

The protein in an egg yolk contains iron which is released as the protein uncoils on heating. Conversely, the egg white protein contains the elements hydrogen and sulphur, which are released as the protein unfolds. The hydrogen and sulphur combine to make the foul smelling substance hydrogen sulphide.

When exposed to prolonged heat, the egg white’s hydrogen sulphide and the egg yolk’s iron then react together to form green iron sulphide. Since the solid yolk separates a little from the egg white, the iron sulphide stays in the space around the yolk. Fortunately it’s not harmful.

To minimize the green ring problem, don’t boil the eggs for longer than necessary. Also, when you remove the egg from the pan, plunge it straight into cold water. The hydrogen sulphide then tends to migrate to the colder shell and away from the yolk.

Hydrogen sulphide has a very strong odour - the classic rotten egg smell. You can sometimes pick up a very faint odour of hydrogen sulphide if you sniff a hard boiled egg. This doesn’t mean the egg is bad. Usually, it’s just the hydrogen sulphide formed from heating the proteins in the egg white.

So next time you hard boil an egg, watch the clock, and make the plunge.

The green hydrogen sulphide layer around a hard-boiled egg yolk is a good example of unavoidable cause and effect relationships that we find throughout nature. When you do x, y results, every time. The only way to keep from getting y is to avoid doing x.

These principles work both positively and negatively for us. We have crops to harvest because we plant. We have green tinged egg yolks because we cook them too long. We get sunburns because we don’t protect ourselves from UV rays. We get relief from pain when we take analgesics.

Sometimes there are things in our lives that distress us. If we look carefully we can occasionally see a cause behind the effect. If we want to change the effect, we need to deal with the cause. That sounds pretty simple, but it’s harder than most of us think. Ingrained patterns of behaviour are hard to change.

But it can be done. Significant positive change is possible. If we’re willing to go back to the causes, we can change the effects.

Many of the things people would like to change about their circumstances are rooted in the psychological or spiritual realms. The non-material has more influence on the material than the reverse. We may not be able to change the material world very much, but we can reduce its negative impact by changing attitudes about it and the degree to which we let it influence us.

Most of us who agree with this idea still struggle to make the necessary changes in the casual areas of life, because its not as easy as it sounds. We have some natural enemies (as well as supernatural ones) that hinder us.

Fortunately for us, God provides spiritual resources which allow us to step beyond the limitations of our own meagre spiritual resources. When we align ourselves in a right relationship with Him, we have access to His moral strength to help us reach our spiritual potential.

David Humphreys and Ron Hughes
© August 2004