Bread staling is caused by starch molecules slowly recrystallizing, not simply by drying out.

The longer version

Staling is largely a matter of starch retrogradation. During baking, starch granules absorb water and their molecules uncoil; as the loaf cools and sits, those chains slowly realign into ordered crystalline regions and squeeze water out. The crumb becomes firm and dry-tasting even though relatively little moisture has left.

The process moves fastest at cool temperatures and pauses when bread is frozen, and gentle reheating temporarily reverses it by loosening the structure again. Wrapping slows moisture loss but does not stop the molecular rearrangement, which is why sealed bread still firms up day after day.

Where this entry sits

Everyday ingredients turn out to be full of quiet chemistry and long history. This collection gathers short, plain explanations of how bread rises, why onions sting, where common spices originate, and how coffee, tea, and chocolate reached the modern kitchen. The full list sits on the Food and Drink page, where every entry is listed in order.