You might be wondering what the title means, what science can a thing as simple as an egg teach us. Read on to know more.
Majority of us like to consume eggs in one form or the other ranging from boiled to poached to fried to scrambled. The dramatic transformation an egg goes through from its liquid raw state to its solid cooked state has always captured my attention and has led me to explore the “whats”, “whys” and “hows” of it. So here I am, sharing with you, my new found knowledge.
An egg consists of 2 parts – the yolk and the albumen. When you crack open an egg, the translucent liquid that you see is the albumen (egg white) that surrounds the generally yellowish yolk. It’s not at all necessary for the yolk to be yellow in shade, it largely depends on the diet the hen is on while laying the egg.
You could imagine these 2 parts to be just sacks of water dispersed with proteins. To completely imagine the structure, you need to know how the proteins look like. Now this is where the science stuff begins. Protein molecules are basically made up of long chains of amino acids bound to one another by fairly weak chemical bonds.
You might have this one doubt, i.e., if the composition of both yolk and albumen are the same, why does the raw yolk seem less runny than a raw egg white? I can say it is because the yolk contains some fat and this fat gets bound with the proteins and keeps them together. The runny nature of egg white can be attributed to the negative electrical charge of the proteins and as you know like charges repel each other. Hence we have the watery and loose egg white. Whereas in the yolk, the presence of fat is strong enough to withstand the repulsive force of the proteins.
Now as we start cooking, the egg gets heated up. All of its molecules start to move faster and collide with one another. As the temperature increases, the collisions become more intense resulting in the breaking apart of the weak chemical bonds holding the amino acid chains together. So now you will be having many short and loose protein strings. With further heat, these become entangled into some kind of a cobweb structure.
You might be wondering what happened to the water part of the egg during all this process? Well, the water has also got dispersed in the protein cobweb so it can no longer flow together, turning the liquid egg into a semi-solid. Continued heating causes more entanglement, leaving less space for the water. Eventually, much of the water is squeezed out (usually referred to as weeping) and evaporates, causing the egg protein to coagulate. When eggs are overcooked, the protein web becomes so tight and retains so little water that the egg white becomes rubbery and the yolk chalky. This difference is due to the fat interspersed with the protein web in the yolk.
So the story of conversion of a liquid to a solid in the presence of heat is the science which an egg has got to teach us all.
That is the end of this post. I would like to know how you feel about this post. Please do leave a comment below.