Understanding Why Sourdough Bread Collapses and Flattens

Sourdough bread that is able to achieve a good rise is susceptible to collapsing and flattening throughout the baking process, in particular during bulk fermentation, shaping/handling the dough, final fermentation and when it is baking in the oven.

This article explains why sourdough bread that is able to rise, suddenly gives up, collapsing and flattening. We will discuss why it happens and what you can do to prevent it from happening.

If you are here because your sourdough bread has difficulty rising, or if your dough feels slack and does not hold its shape well, we are talking about a different problem. Read these articles instead:

UItimate Guide to Achieving the Perfect Rise in Sourdough Bread

Why Sourdough Feels Loose and Does Not Hold its Shape?

8 Reasons why sourdough bread collapses and flattens

1. Over risen sourdough during final fermentation/proofing

Sourdough that is over fermented will collapse. This is because fermentation rate and gas production rate has gone past its peak as the yeast and bacteria runs out of food needed for the fermentation reaction at a certain point. Carbon dioxide gas production is reduced to the point where the dough is unable to stay inflated and eventually the dough collapses.

Aim to proof the dough up to 90% rise during the final fermentation stage before it enters the oven. Loading the dough at 90% rise ensures that there is still enough simple sugars left for the dough to rise during oven spring that happens in the hot oven.

If the dough enters the oven at 100% rise, it will inevitably collapse because the bacteria and yeast does not have enough simple sugar to sustain the fermentation reaction, carbon dioxide gas production reduces and dough collapses.

During cold retardation of the dough at a lower temperature, ideally we would allow the dough to warm up to room temperature before loading it into the oven. However, more importantly if the dough comes out of the retarder at a fully risen state, we should immediately load the cold dough into the hot oven to prevent flattening or collapsing of the bread. Adding a few minutes to the total bake time will counteract the initial cold dough temperature.

It takes experience to know when the dough is at 90% rise. One way to speed up this learning process is to intentionally allow the dough to over proof and collapse while recording the time taken. From that point, we can subtract about 15-20 minutes to arrive at the ideal proofing time.

2. Excessive fermentation time when baking with higher percentage of starter

There are some scenarios that causes the dough to ferment at a much faster rate, and we should reduce fermentation time in this cases. Failure to do so will result in a dough that goes past the point of 100% rise and collapse.

We should reduce total fermentation time when:

  • Fermenting at a higher temperature – Yeast and bacteria metabolizes and carries out fermentation at a rate that is directly proportionate to temperature; the higher the temperature the faster the rate of fermentation, and the quicker the dough takes to reach full fermentation.
  • Using a higher percentage of starter – Dough that contains a higher percentage of starter ferments more rapidly due to the greater initial number of yeasts and bacteria in the dough. It reaches its point of 100% rise more quickly than dough that contains a lower percentage of starter.
  • Baking with higher hydration dough – Dough that contains higher hydration (water content) ferments more rapidly as the flour is more deeply hydrated which helps the yeast and bacteria to easily metabolize and carry out fermentation.
  • Baking with higher percentage of Rye flour – Rye flour has a high content of soluble sugars. Soluble sugars are the food source for the fermentation reaction. A high initial content of these soluble sugars means that fermentation happens rather rapidly. This in combination of rye’s inability to form gluten means rye doughs can easily over ferment and collapse.

Fermentation starts when all the ingredients are combined during mixing, and continues to ferment even in the hot oven during baking for the first 10 minutes or so; this is because yeast and bacteria that undergoes fermentation only dies off at 50-60 Celcius.

When reducing total fermentation time, we should consider reducing the total time of bulk fermentation, bench rest time and the final proofing time before the loaf is scored and enters the oven.

3. Excessive and insufficient bench rest time

The purpose of bench resting is to allow the dough to relax after pre-shaping to reduce the tendency for the dough to tear during the final shaping process.

If the dough does not have sufficient bench rest time, the outer skin of the dough can still be in stiff and brittle state that tears easily during shaping. When the skin tears, the dough looses tension and collapses on itself.

Additionally, if left to bench rest for too long, the dough can slacken excessively, flatten and does not hold its shape well.

Bench rest shouldn’t be longer than 20 minutes, which is usually enough time for the dough to relax to reduce the risk of tearing, but still be sufficiently taut for holding its shape during final shaping.

4. Rough handling of the dough

Dough that is mishandled can collapse and flatten from being torn, being degassed excessively or both.

Even when the dough has been given the appropriate amount of bench rest time, a rough handling of the dough can tear the skin of the dough. The skin of the dough is in tension and this tension helps to hold the shape of the dough, when torn the dough loses its strength and collapses.

Sourdough bread made with very high hydration levels at more than 75% baker’s percentage such as the ciabatta or pan de cristal relies on the retainment of the carbon dioxide gasses from the fermentation reaction to hold its shape. Rough handling of very wet dough can degas the dough too much, causing it flatten and never recovers in volume.

Be gentle when working with the dough and always use wet hands when handling the dough to prevent it from sticking, tearing and collapsing.

5. Excessively deep scoring on weak sourdough bread

On weak bread, such as those that has over risen, or sourdough breads with high proportion of rye flour, light scoring is only needed. Deep scoring will likely make the bread flatten out rather than rise upward, as the lateral structure of the loaf is not strong enough to support the weight of the dough.

Strong bread that has risen to the optimal degree can handle more vigorous scoring and their cuts will expand beautifully in the oven.

6. Excessive steaming

Steaming helps to moisten and keep dough’s surface temperature low during the bake so that it has the time to fully rise before the hard crust is formed.

Steaming when done right, allows the dough to rise fully in the oven and the hard crust to set at a point just before the dough achieves a 100% rise so that the baked loaf maintains its high volume shape.

When there is too much steam in the oven, the formation of the crust is delayed excessively and the loaf has gone past the point of 100% rise and collapses before the hard crust can set to hold its shape.

If you are loading a dough that has fully risen into the oven, reduce steaming. Otherwise, it will cause the loaf to collapse during the bake.

7. The use of spring wheat flour with an extended fermentation period

Spring wheat makes high gluten flour with protein levels at about 13-15%, while winter wheat makes flour of about 11-12% protein.

Although the protein content of spring wheat flour is higher than winter wheat flour, the quality of the protein in spring wheat flour is inferior to the quality of protein in winter wheat flour.

If you use spring wheat flour in combination of a long and slow fermentation period, the dough tends to lose structure and stability during the fermentation and the bread is likely to flatten.

Winter wheat is more resistant to this weakening effect and is superior to spring wheat when baking over an extended fermentation period.

8. High percentage of damaged starch

The grain kernel of our flour goes through a harsh milling process that inevitably leaves some starch molecules to split open. These broken starch molecules are known as damaged starch. All flour has damaged starch but when damaged starch in flour is greater than 10%, it will have negative effect on dough strength.

Problems with damaged starch comes from the over absorption of water. Damaged starch absorbs water during mixing as opposed to undamaged starch where the water merely coats the outer surface.

The water absorbed by the damaged starch is then gradually released after mixing and the dough structure weakens, which causes loaves to become slack at the end of mixing and flatten out during shaping.

If you have tried everything else on this list and your sourdough is still collapsing, your flour may be the issue.

If you are using American made flour, try switching to European flour. American flour has about 8-9% starch damage, while European flour has about 7% starch damage.


Hey there! I'm Sam, your go-to pal for all things sourdough. I've been baking and kneading for 10 fun-filled years, and I can't wait to share the joy of turning simple ingredients into heavenly sourdough bread with you. Grab your apron and let's dive into this amazing world of sourdough bread together on this blog.

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