Why are some hardboiled eggs more difficult to peel than others?

Question

I follow the [rolling technique](https://www.youtube.com/watch?v=qLjCDNoRC-g) to crack all my eggs. Most of the time the shell splits into 2 easily separable pieces. Every so often the technique fails and rolling the egg results in very small cracks making it very difficult to peel. Is it the way I’m boiling/storing/cracking the eggs? Please ELI5.

In: Biology

Answer 1

As time goes by the dissolved CO2 in the keratin (the substance that binds the shell to the albumin) inside the egg is released from the egg which loosens the keratin’s hold on the shell up a good bit. Try boiling your eggs about five days after you buy them.