The crust of the sourdough bread takes on an unpleasant hard rock-like texture when it is excessively dry and thick; a dry but thin crust on the other hand produces a pleasant crispy crust.
There are many factors in the baking process that can cause a dry and thick crust, resulting in the undesirable hardness; we will explore what these factors are so that you can avoid them in your bake.
What makes crust hard (excessively dry and thick)
1. Insufficient gluten development
Mixing aligns the glutenin and gliadin proteins in your flour to form gluten networks which functions to trap carbon dioxide gasses from the fermentation, which enables the loaf to gain volume and rise.
When gluten is developed only minimally, there are less layers in the dough where carbon dioxide gasses are trapped, and as such the dough is dense under its skin. When baked, this dense dough sets and hardens into a dense, thick and hard crust.
If gluten is developed to the highest degree, there are many layers in the dough that is able to trap carbon dioxide gasses, and when the dough rises, the area under the skin of the dough is less dense and filled with air holes. When baked the thin skin sets and hardens into a crispy crust.
2. Excessive moisture loss during baking
The rate at which moisture is lost in the oven plays a big role in the dryness of the crust. The more moisture is loss during baking, the drier the crust becomes which contributes to a harder crust texture
Here are some of the factors that affects the moisture loss during baking:
- Overall loaf weight
- Smaller dough pieces tend to lose a higher proportion of their initial moisture weight due to a higher surface area to volume ratio. A larger dough has more surface area than a smaller dough, but a larger dough also has a much greater internal volume. Therefore larger shaped dough losses less moisture to evaporation.
- Dough shape
- Long skinny loaves such as baguettes have higher surface area which loses a higher amount of moisture than the same dough weight shaped into a round loaf. The higher surface area of long skinny loaves results in a greater loss of moisture to evaporation.
- Length and temperature of bake
- The longer you bake, overall loss of moisture becomes greater. The higher the temperature of the bake, the quicker the moisture is loss to evaporation. If you are baking at a very high temperature over a long duration, the crust will burn. If you are baking at a lower temperature, over a longer duration, the surface of the dough losses a great amount of moisture without burning, leading to a thick and dry crust that feels very hard.
- Typical duration of bake ranges from 25 – 45 minutes at 232 Celcius; a higher hydration dough requires a longer bake time and a heavier loaf also calls for a longer bake time.
3. Insufficient cooling time
As the hot loaf leaves the oven, a lot of its moisture is trapped in starch molecules of the bread’s crumb. Sufficient cooling time allows some of these moisture to dissipate out of the starch molecule in the crumb of the bread, which will then be absorbed by the dry crust, softening it.
When we do not cool the bread sufficiently before slicing, not enough time has passed for the moisture to be absorbed by the crust, causing the crust to remain dry and hard.
It is best to allow sourdough bread to cool for at least 4 hours at room temperature for the moisture to fully settle and flavor to fully develop. Premature cooling causes a dry and hard crust with compromised flavor.
Proper cooling times is dependent on the size of the loaf, shape of the loaf, the room temperature and the type of flour used. I have written a comprehensive guide on cooling sourdough bread which explains how all these factors affect cooling times.
If you would like to learn more, read Proper Cooling To Get The Cleanest Cuts On Sourdough Bread
4. Inadequate steaming
Steaming is often introduce to sourdough bread to control the timing at which the crust is formed.
As more steam is used, the formation of the crust is delayed as steam lowers the surface temperature of the dough, resulting in a thin crust.
If no steam is used, the formation of the crust happens rapidly over a longer period as the surface temperature of the dough is higher, resulting in a thicker, drier and harder crust.
We typically steam until the crust takes on a rich brown coloration, then the oven is vent to release all the steam and the loaf finishes its bake in a dry environment to achieve a thin, dry and crispy crust. If we do not vent the oven, the resulting crust will be thin but wet and chewy as the high moisture content in the steam prevents the crust from hardening.
5. Exposed dough during final proofing
Always cover your dough with a plastic sheet to prevent excessive air flow around the dough during final proofing which can dry the surface of the dough forming a premature crust to form before the dough even enters the oven.
This premature crust acts as an additional layer of crust to be form on top of the crust developed during the bake and causes the final crust to be thicker, drier and harder than usual.
How to soften a crust that is already hard?
1. Cover the baked loaf while it is cooling
We can retain whatever moisture is left after the bake by covering the baked loaf as it is cooling. This minimizes drying and any further hardening of the crust.
2. Line the loaf with a damped paper towel
The damped paper towel retains moisture and also introduces additional moisture that will be absorbed by the crust. Be careful not to overdo this as too much moisture can result in a soggy crust.
3. Puncture the hard crust with many tiny holes
Take a thin and sharp piece of metal (cake testing stick works fine) and punch in many small holes that run through the entire thickness of the crust; we are talking about a 100 to 200 small tiny holes. It is the same method the Chinese use to make crispy pork belly.
This method makes the hard thick crust crispier as the small holes reduces the overall density of the crust and allows the crust to crumble and break easily into tiny pieces when bitten. The resulting texture is likened to biting into a very crunchy thick cracker.