Alkali flips sticky patches out and they knit a net, with no heat.
Full mechanism, in text
Key knowledge · how alkali turns an egg into a century egg
1 · Why the white is liquid in the first place
Egg white is liquid because its proteins are rolled into balls with the sticky parts hidden inside, so they cannot stick to each other.The proteins in egg white are little rolled-up balls, hydrophilic parts facing out, the parts that would stick carefully hidden inside. Nothing can grab anything, so they float in water, each going its own way — that is a liquid.
2 · Alkali flips the patches out, then they knit a net
Strong alkali charges protein surfaces so they repel and flips the sticky patches out so they hook, knitting a loose net that locks in water: a gel.Strong alkali does two things: it charges the surfaces so they push apart, and it flips the sticky patches onto the outside. Broad faces repel, patches hook — a loose network, water locked in the mesh. That is a gel. None of this needs heat.
3 · It is not cooked; it is set by alkali
Heat shakes proteins apart into a messy, opaque hard mass, while alkali hooks them at specific points and keeps the backbone, giving a translucent, springy gel.Heat works by shaking apart: they stick wherever they meet, the net is dense and messy, light cannot pass — an opaque white hard mass. Alkali hooks at specific points: the backbone is still there, the mesh is regular, light can pass — a translucent, springy gel. Cook it too long and you stack a second, messy heat-net on a net that was already joined.
4 · Savor, ammonia, and green yolk are three exits of one breakdown
Alkali takes protein apart: amino acids give savor, nitrogen groups become ammonia, and sulfur amino acids release hydrogen sulfide that reacts with yolk iron to form dark-green iron sulfide.Protein is taken apart in alkali. Free amino acids give savor; nitrogen groups come off as ammonia; sulfur amino acids release hydrogen sulfide, which meets iron in the yolk and makes dark-green iron sulfide. How deep the green is records how long the breakdown has run; it cannot tell you whether there is lead. That depends on the process and the source: the patterning and the gel need metal ions, not necessarily lead, and modern licensed processes mostly use copper or zinc instead; with licensed brands, the everyday thing to watch is sodium.