The Chemistry of Food and Cooking : Eggs.

In cooking, everything is chemistry! Whether you knead bread, bake a pie, or roast a meat, chemical reaction is taking place. Not only with these foods, but with others such as eggs. Egg proteins change when you heat them, beat them, or mix them with other ingredients. Being able to understand these changes can help you understand the roles that eggs play in cooking. The proteins in an egg white are twisted, folded, and curled up into a circular shape. Different kinds of weak chemical bonds keep the protein curled up tight in the water that surrounds it.

When you apply heat an egg, you aggravate the egg-white proteins, and you make them bounce around. They slam into the water molecules that surround them and bash into each other. All of this bashing around breaks the weak bonds that kept the protein curled up. The egg proteins uncurl and bump into other proteins that have also uncurled. New chemical bonds form and these bonds connect one protein to another. After all of the bashing and bonding stops, the egg proteins that were separated from each other, are no longer like that. They then form a network of connected proteins. The water that the proteins floated in, is now captured and held in the protein web. If you leave the eggs at a high temperature too long, too many bonds form and the egg white becomes rubbery.

When you beat raw egg white to make a souffle, you send air bubbles into the water protein solution. Adding air bubbles to egg whites unfolds the egg proteins just like heating them. The reason why air bubbles makes egg proteins uncurl is because of the amino acids that make up proteins. Some amino acids are attracted to water, other amino acids are repelled by water. Egg whites contain both kinds of amino acids. When the protein is curled up, the water repelled amino acids are packed in the center away from the water and the water attracted amino acids are on the outside closer to the water. When an egg protein is up against an air bubble, part of