Onions are some of the most interesting vegetables on the planet. As a very famous ogre once said, “onions have layers”—but we’re about to take things even deeper than that. Why is it that onions are so bitter when they’re uncooked, and yet so sweet once they’re deliciously sautéed? Let’s dive into the mystical process of onion-cooking.
Sulfur Compounds
Sulfur compounds are the main reason that onions have such a strong and bitter taste when they aren’t cooked. However, all of that changes when the onions is exposed to intense heat.
Caramelization
Onions actually contain plenty of sugars, but they aren’t exactly sweet when they’re raw. The chemical reactions that occur when you start to cook an onion lead to something called caramelization, which makes those sugars much sweeter like we’re accustomed to.
Maillard Reaction
There’s also something called the Maillard reaction, which happens when the reduced sugars combine with amino acids. This reaction also creates a much deeper and richer flavor within the onion.
Softening The Onions
If all of that’s not enough, the cooking process also softens the onions, making them less rough and much more palatable for us. When you combine all of these factors together, a cooked onion becomes essentially a completely different element than it was before.
