Why does bread get hard?
Hard bread doesn't taste good - everyone knows that. But which microscopic processes actually ensure that bread becomes hard in the first place? Chemistry provides some of the answers - and shows what it is better not to do with bread.
What you need:
- some time and patience
- as well as an interest in science
Stale and hard bread - what happens there?
- The crispy crust of a bread and also of bun suffers quickly - everyone has had this experience.
- As soon as the bread comes into contact with moisture, especially the air, the crust is softened. A little while ago it was still crispy - now rather slack: The air also contains a small amount of water vapor, which quickly causes rolls in particular to lose their freshness.
- This upper moist layer will dry out over time - the water molecules will evaporate. But why is bread always hard and stale in the middle?
- Contrary to popular belief, stale or even hard bread is not (only) made through Drying out, at least not primarily, but rather as a consequence of hardening, are other processes responsible.
- Bread also becomes stale and often even hard when it loses its liquid. This was already shown by experiments in the 19th Century, where sealed loaves of bread were used.
- Bread (and also rolls) consist for the most part of swollen starch molecules of the used grain. In the course of storage, however, these starch molecules change, they swell and crystallize out. During this transformation, they bind part of the water that has been released into a new, but much denser structure - the bread becomes hard on the inside and appears dry. Free water molecules that wet it are no longer there.
- However, many of the released water particles wander around (initially) in the bread. In doing so, you will also reach the - at least initially - still dry crust. They are literally drawn to where they are absorbed. You know the result: the crispy crust becomes leathery.
- And if you have not kept the bread in a sealed form or covered it, the water molecules will evaporate from the crust.
- These processes explain why fresh bread initially forms a rubbery crust, but then becomes completely hard (also inside).
Freezing bread properly - you should pay attention to this
Bread tastes best when it's fresh on the table. But already on ...
Hard bread - what to do?
This aging process of the bread, which was caused by humidity and the new structure of the starch, can be reversed (at least within limits):
- Spray the surface of the Loaves of bread and rolls easily with water and bake them up - a trick that every "Sunday baker" knows.
- However, a very low temperature of around 60 ° C is sufficient and of course works better with bread rolls than with larger breads.
- Or you can dip sliced hard bread in coffee or milk a - the capillary effect pulls the liquid through the fine passages in the bread.
- Incidentally, a little oil or fat in the bread can slow down these aging processes because the fat molecules prevent the binding of water molecules into the new starch crystals.
- Perhaps interesting for people who like to put their bread in the refrigerator: The starch crystallizes out best at 4 ° C, one reason why bread in the refrigerator becomes stale, hard and dry particularly quickly! And often in a few hours.
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