How a liquid egg white becomes a gel
An eggshell looks solid, but it has tiny pores that let gases and moisture pass through. During curing, alkaline ingredients in the coating gradually affect the egg inside. The change is slow: the mixture does not simply dye the white dark from the outside. It alters the proteins that give raw egg white its runny texture.
Proteins are folded molecules. In a strongly alkaline environment, their structure shifts, exposing parts that can link with one another. As these connections build, they form a network that traps water. The result is a firm, translucent gel—much like a set jelly, but made from egg proteins rather than gelatin.
The yolk changes differently
The yolk contains more fat and other materials than the white, so its texture and color develop along a different path. It can become soft and creamy at the center, with darker green or gray tones. Sulfur compounds formed during curing help account for the characteristic smell; reactions involving sulfur and minerals in the egg also contribute to its color.
That contrast is part of the appeal: one egg can hold a clear, springy white around a rich, almost custard-like yolk. The cure transforms the egg’s texture as well as its appearance, without cooking it in the usual way.
Why the name is misleading
A century egg is not left to age for a hundred years. It is cured long enough for the alkaline mixture to penetrate and for the proteins to set. The exact time depends on the method and conditions, but the key is controlled chemical change: the egg is preserved by shifting its internal environment, not by waiting for it to decay.
