Frozen bread turns damp and rubbery when thawed because of the ice crystals that form within its starch structure during freezing. As these crystals grow, they physically break the walls of the starch cells and disrupt the bread's normal texture.
What makes the dampness worse?
During thawing, these damaged areas release their trapped moisture unevenly; some spots end up overly wet while others stay dry. This uneven distribution is what gives the whole loaf a rubbery, damp texture.
Thawing bread quickly at room temperature inside a sealed bag also makes the problem worse; steam trapped inside the bag cannot escape and condenses on the surface of the bread, adding an extra layer of dampness.
What prevents the dampness?
Leaving the bag slightly open while thawing lets the steam escape and greatly reduces the moisture that builds up on the surface.
Instead of thawing slowly, heating the bread directly in a toaster or a preheated oven for a few minutes both speeds up the thawing and evaporates excess surface moisture, helping the crust turn crisp again.
Slicing the bread before freezing also improves the result; sliced bread thaws far faster and more evenly than a whole loaf, which helps the moisture distribute more evenly.
Wrapping the bread tightly and airtight before freezing also helps keep the ice crystals smaller; crystals form larger and more destructive on surfaces exposed to air.
Keeping the freezer's temperature steady is a factor too; opening and closing the freezer door often causes small temperature fluctuations, and those fluctuations contribute to the ice crystals growing larger over time.
Refreezing bread once it has thawed is not recommended, since it recreates the same ice crystal problem a second time; thawing only the amount that will actually be used gives a better result.
The type of bread also affects the outcome; airy, crusty breads like baguettes tend to form more ice crystals during freezing, since their large holes hold more air and moisture; tight-crumbed sandwich bread is relatively less prone to this problem.
Bread left in the freezer for a long time can also develop what is called "freezer burn", separate from the ice crystal problem; in that case, moisture evaporates completely from parts of the surface, leaving dry, tough patches that feel harder and different in texture from the rest of the loaf once thawed.
Some bakers prefer to wrap bread in a clean kitchen towel and thaw it at room temperature; the towel absorbs moisture better than a plastic bag, reducing surface dampness and giving a more even thaw.