Why Does Bread Stale Faster in the Fridge?

Bread becoming firm is often described as “losing moisture”, but that is only part of the story. In freshly baked bread, starch has absorbed water and formed a soft structure. As the loaf cools, starch molecules gradually realign into more ordered regions, a process called starch retrogradation. Water is also redistributed between the starch and gluten network, so the crumb loses its softness.

The temperature of a domestic fridge, around 4°C, allows this realignment to proceed relatively quickly. Bread can therefore become firm faster than it would at room temperature even when it is tightly wrapped and has not obviously dried out. That does not make refrigeration useless: low temperatures slow mould growth, but preventing spoilage and preserving softness are different aims.

If bread will be eaten within a day or two, sealing it and keeping it at a suitable room temperature will usually preserve its texture better. For longer storage, freezing individual portions is often preferable to refrigeration. Freezing greatly reduces molecular movement, and thawing or brief reheating can partly restore softness, although it cannot reverse every change involved in staling. The rate also depends on the recipe, moisture content, acidity and packaging, so “the fridge makes every bread stale at the same rate” is only an approximation.

https://pubmed.ncbi.nlm.nih.gov/39870278/
https://www.mdpi.com/2304-8158/13/4/517