Spheres Within Spheres

That’s a yolk by numbers and nutrients. But there’s a lot more to this concentrated pool of the sun’s rays. Its structure is intricate, much like a Chinese set of nested spheres carved from a single block of jade. We see the first layer of structure whenever we cut into a hard-cooked egg. Where heat gels the white into a smooth, continuous mass, the yolk sets into a crumbly mass of separate particles. The intact yolk turns out to consist of spherical compartments about a tenth of a millimeter across, each contained within a flexible membrane, and so tightly packed that they’re distorted into flat-sided shapes (much like the oil droplets that egg yolk stabilizes in mayonnaise). When a yolk is cooked intact, these spheres harden into individual particles and give the yolk its characteristic crumbly texture. But break the yolk out before you cook it so that the spheres can move freely, and it becomes less granular.