The Chemistry Behind Egg Yolks!

Hey guys! Welcome back.

On my last post, I wrote about egg whites and the chemistry behind them. Then I started wondering.... some recipes ONLY require egg yolks! Why is this?

Many recipes like creme brulee, ice cream, hollandaise, mayo, and other heavily cream based foods require only egg yolks. While this might be because the yolk contains all the cholesterol and protein and makes the dish extremely creamy, there is also tons of science behind this cool reaction.

Everyone knows that, left to their own devices, oil and water don’t mix. But for many recipes, you mix oil-based and water-based liquids—and want them to stay that way. Often, egg yolks come to your rescue by creating an emulsion.

Most food emulsions are known as the oil-in-water type, which means that oil (or fat) droplets are dispersed throughout the water. Put oil and water in a jar, shake it vigorously, and you’ll disperse the oil. To prevent the oil droplets from coalescing, however, a substance known as an emulsifier is required. Egg yolk contains a number of emulsifiers, which is why egg yolks are so important in making foods such as hollandaise and mayonnaise.

Many proteins in egg yolk can act as emulsifiers because they have some amino acids that repel water and some amino acids that attract water. Mix egg proteins thoroughly with oil and water, and one part of the protein will stick to the water and another part will stick to the oil.

Lecithin is another important emulsifier found in egg yolk. Known as a phospholipid, it’s a fatlike molecule with a water-loving “head” and a long, water-fearing “tail.” The tail gets buried in the fat droplets, and its head sticks out of the droplet surface into the surrounding water. This establishes a barrier that prevents the surface of the fat droplet from coming into contact with the surface of another fat droplet. Next time you use mayo on your bread, or crack the shell of a creme brulee, maybe you'll think of the chemistry behind it!

Thank you all for reading! Tune in next week for another food packed chemistry article!! :)

Insert pics of delicious looking creamy foods ;-)