system
Given the following post, respond as if you're commenting on Reddit:
human
Why does food, like pretzels and bread, go stale?

And does stale food have less nutrients than when it was fresh? Thank you.
gpt
Bread goes stale because of a phenomenon known as *retrogradation*, where the starch molecules align and crystalize. This binds water and leads to the firm, dry texture that we associate with stale bread. It's the same process that makes leftover rice tooth-crackingly hard.

Hard pretzels are baked down to an extremely low moisture content to give them the crunch and crisp we expect. When exposed to a generally humid atmosphere, they will absorb enough water to begin retrogradation as mentioned above.