Bread kept in a refrigerator turns firm and dry within a day or two, faster than the same loaf left on a counter. Staling is not the same process as drying out, and cold speeds it up.
Staling is starch recrystallising
During baking, starch granules absorb water and swell in a process called gelatinisation, which gives fresh bread its soft, open texture.
That arrangement is unstable. As the loaf cools and ages, the starch molecules gradually reorganise into a more ordered crystalline structure and squeeze out the water they were holding.
The result is a crumb that feels dry and firm even though the water is still inside the loaf.
The reorganisation is fastest just above freezing
Retrogradation has a temperature preference, and it proceeds most rapidly in the range a domestic refrigerator maintains.
Room temperature is warm enough to slow it noticeably. Freezing is cold enough to stop it almost completely, because molecular movement effectively halts.
A refrigerator sits in the worst part of that range, which is why it is the least effective place to keep a loaf.
Reheating reverses part of the change
Because staling is a physical rearrangement rather than spoilage, warming stale bread partly undoes it. Heat returns the starch toward its softer state.
This is why a day-old roll warmed in an oven tastes close to fresh, and why toasting improves bread that has firmed up.
The improvement is temporary, and it accelerates once the bread cools again, so reheating works only once or twice.
The freezer is the correct storage answer
Freezing a loaf on the day it is baked preserves the fresh texture, and thawing at room temperature restores most of it.
Slicing before freezing is practical, since individual slices can be toasted directly and the rest of the loaf is never exposed to warming and refreezing.
Wrapping matters mainly to prevent the surface losing moisture to the freezer, which is a separate problem from staling.
Mould is the trade-off the fridge is solving
Refrigeration does slow mould growth, which is why it seems sensible in a humid kitchen.
The choice is therefore between faster staling and slower spoilage, and for a loaf that will be eaten within a few days the counter usually wins. Bread with high moisture or added fillings is the exception, since it spoils before it stales.