I don’t mean melting things like cheese or butter, but like a tortilla that is more rigid at room temperature, and then fluppy when heated (before crisping up when heated more).
In: Chemistry
It isn’t restricted to food. Everything softens when heated.
Excited (hot) molecules or atoms move around more easily because they aren’t as attached to each other when they’re cold. They’re bouncing off each other and can escape, or at least change position much more easily.
Cold molecules/atoms are stuck to each other and don’t want to move easily unless a lot of energy is applied. Which is heat.
Actually, tortillas soften for the same reason that cheese or butter do.
Tortillas contain lard, a fat. That at higher temperatures melts, but since the fats are mixed in and contained within the gluten matrix of the flour, it doesn’t just flow out. But it does cause the tortilla to become softer and more flexible. And that is the case for most foods that have fats mixed into them.
But if you continue to apply heat, you get the Mallard Reaction. This is a chemical reaction between amino acids and sugars which leads to the caramelization of new sugars created by the reaction, which is why things brown when you cook them. The caramelized sugars also harden, which if you have enough of it will crispen your tortilla.
The cells of fruits and vegetables contain a type of sugar called Pectin. It is sort of like jello, in that it forms a gel and in the right arrangement it can be quite hard. But when heated up the gel breaks down and this causes fruits and vegetables become soft and mushy when cooked.
There are a couple reasons. In some cases there are components that become less rigid when warmed. In tortillas there is often some fat that will heat up and become softer.
Another reason is that any existing water will turn to steam and make things softer. Like steaming wood to bend it.
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