Sourdough Bulk Fermentation 101

Bulk fermentation is one of, if not the most important and misunderstood stages in sourdough bread baking. Sourdough bread develops much of its flavor, crumb structure, and rise during bulk fermentation.

Without a proper sourdough bulk fermentation, the sourdough will not be proofed correctly, which will lead to a dense or flat bread.

This extremely detailed sourdough bulk fermentation guide will cover many of your questions as to why bulk fermentation is important, how to control bulk fermentation with temperature, and various indicators to know when bulk fermentation is finished.

Don’t forget to leave your bulk fermentation questions or your own bulk fermentation tips in the comments at the end of the post!

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What is Bulk Fermentation?

Bulk fermentation is the first proofing stage between mixing and dividing or shaping dough.

Other words of describing bulk fermentation are first rise, first proof, bulk rise, or bulk proof.

This stage is called bulk fermentation because many bread bakers and bakeries ferment large amounts of bread dough at a time. As a home baker, you might make only one or two loaves at a time, but the same idea applies.

When bulk fermentation is complete, the dough is divided, shaped, and proofed again before baking.

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Why is Bulk Fermentation Important?

Bulk fermentation is important because it is the proofing stage when the dough is accumulating gases, which will determine the structure and flavor of sourdough bread.

The gluten network you develop from mixing will trap the carbon dioxide produced during bulk fermentation. This will result in the light texture and fluffy interior associated with sourdough bread.

The large, even holes and soft, custardy interior texture of sourdough bread are often called an “open crumb” and are an aspiration of many sourdough bakers. An open crumb can only be achieved with a proper bulk ferment.

Successful bulk fermentation can also help achieve the sought-after “sourdough ear“, which is one sign of a properly proofed bread.

Proper fermentation is crucial in sourdough baking. But even with the best ingredients, tools, and experience, if you misjudge bulk fermentation, your dough can turn out under- or over-proofed.

See this bulk fermentation chart to determine if your dough is properly fermented.

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What Do You Do During Bulk Fermentation?

Sourdough bulk fermentation is the longest room temperature stage in sourdough baking and it’s also the most difficult stage to gauge for most people.

Bulk fermentation is largely hands-off as you simply allow the bread dough to ferment on its own schedule. But there are some actions that are taken periodically during bulk fermentation as well which are described below.

I typically proof my dough in a covered mixing bowl, but if you’re making large amounts of bread, it might be helpful to invest in a bulk fermentation container. I recommend this 6-quart storage container for a good bulk fermentation container if you’re proofing many doughs. There are various sizes as well including a larger 8-quart container.

What Are Stretch & Folds or Coil Folds?

Many bakers employ stretch & folds or more gentle coil folds like in My Everyday Sourdough Bread Recipe, Buckwheat Sourdough, or Spelt Sourdough Bread recipes during bulk fermentation.

Performing a series of folds during bulk fermentation will help regulate dough temperature, further gluten development, and help you sense how quickly your dough is fermenting.

Either type of fold will be beneficial for your dough. Some bakers have a strong preference for one or the other. I tend to use gentle coil folds during bulk fermentation because I feel like it keeps the integrity of gases more intact which helps achieve a more open crumb.

How Many Stretch & Folds or Coil Folds For Sourdough?

The number of folds and the length of sourdough bulk fermentation time depend on the recipe you’re using and from dough to dough. You’re looking for a balance between how elastic and extensible your dough is.

If there are too few folds, your dough might be too slack during shaping and may flatten during baking. Too many folds and your dough may have a tight crumb structure.

The more you bake, the more you’ll develop a sense of when bulk fermentation is complete and if your dough needs more or fewer folds.

Since stretch & folds are slightly stronger, a set of 4 to 6 stretch & folds in many sourdough recipes is common. For gentle coil folds, 6 to 8 sets is is typical. Some recipes may use both or another method entirely (like a slap and fold technique).

Check out my YouTube video for how to perform coil folds during bulk fermentation below.

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How Do You Control Bulk Fermentation?

The best way to control bulk fermentation is to keep your dough at a constant temperature throughout bulk fermentation.

Sourdough bulk fermentation is best in a slightly warmer than room temperature environment at 75-80ºF or 24-27ºC.

However, controlling dough temperature can be difficult if you live somewhere with fluctuating temperatures and seasons like I do in New England.

Below are a couple of my favorite tools I use and recommend to control bulk fermentation temperature:

• Brød and Taylor Proofer:
  • The folding proofer is large enough to hold a sourdough starter container and a medium mixing bowl for proofing at the same time.
  • The proofer can be kept at a temperature range of 70-195ºF (21-90ºC). I keep my proofer at a cozy 78ºF which is ideal for sourdough yeasts during bulk fermentation and my sourdough starter.
  • Regulating my dough temperature using the proofer, especially during cold, winter months has resulted in much more consistent sourdough bakes for me and overall better sourdough bread.
• Thermoworks Classic Super-Fast® Thermapen®:
  • Use the Thermapen to check dough temperature throughout bulk fermentation.
  • The instant-read thermometer is by far the most accurate and best-performing cooking/baking thermometer.
  • Simply stick the thermometer into your dough and it will tell you the temperature of your bread in a literal second.
  • I use my Thermapen for so many kitchen tasks and couldn’t recommend investing in one enough.

Another factor that affects fermentation is the hydration of the dough, and whether whole wheat flours are used.

For example, a dough with a high hydration like my 100% hydration Sourdough Pan de Cristal recipe will proof faster than a lower hydration bread.

Likewise, whole wheat flours have nutrients that sourdough yeasts love. You’ll notice if you use large amounts of whole wheats in a recipe like my Seeded Whole Wheat Sourdough Sandwich Bread or Soft Sourdough Rye Sandwich Bread, that bulk fermentation accelerates.

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How Long Does Bulk Fermentation Last?

Bulk fermentation can typically last anywhere from 3.5 to 7 hours depending on the dough temperature, recipe, and amount of sourdough starter used.

At 78ºF, bulk fermentation usually lasts about 4-4.5 hours for my typical sourdough bread. If colder or if using less sourdough starter in a recipe, bulk fermentation might take longer.

A sourdough cold bulk fermentation is not recommended, as the cold temperatures will not proof the dough adequately. Instead, proof the dough in the fridge overnight after it has already been shaped. This is called a retard or cold proof.

The range of time it takes for bulk fermentation to be complete is broad because there are so many factors that affect how quickly your dough ferments.

Factors that impact sourdough bulk fermentation time include but are not limited to:

• The strength of your sourdough starter (see tips to strengthen your starter)
• Ambient temperature
• The types of flours or other ingredients used
• Humidity
• Elevation (higher elevation=less bulk fermentation time).
• If you autolyse your bread or not

For example, added sugar can accelerate bulk fermentation, like in my Calabrian Chili and Honey Sourdough Bread. The sourdough yeasts in this recipe consume the honey as sugars at a faster rate than a typical loaf.

Enriched doughs with eggs, milk, and butter like Sourdough Brioche Bread or Sourdough Cinnamon Rolls may take longer.

While documenting the length of time bulk fermentation takes can be helpful, it is not the most accurate measure of when bulk fermentation is complete.

Instead, sensory indicators are the best signals to know when bulk fermentation is done. Use time as a guide and not as the only indicator.

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When is Bulk Fermentation Done?

Knowing when sourdough bulk fermentation is complete can be challenging at first.

With more sourdough baking experience, you will develop a better intuitive sense using sensory clues of when your dough is finished proofing.

Signs That Your Dough is Finished Proofing:

The chart below highlights general signs and indicators to know if your sourdough is proofed correctly or under/over-proofed at the end of bulk fermentation. I also include photos below of various bulk fermentation stages.

Always refer to the indicators used by a recipe as they can vary from these.

Proofed Correctly	Under-proofed	Over-proofed
The dough has grown about 50% in size (refer to recipe).	The dough has only grown slightly in size.	The dough might be doubled or more in size (refer to recipe).
The dough has visible gas bubbles on top of and throughout the dough.	There are no visible gas bubbles.	The dough has many gas bubbles. Some bubbles deflated.
The dough is jiggly when you shake it.	The dough is stiff and does not jiggle.	The dough will be very jiggly and slack.
The top of the dough is domed and smooth.	The top of the dough is flat and rugged.	The top of the dough is extremely poofy and might overflow the proofing container. To the extreme, it will be deflated.
The dough feels aerated and full of air. Generally easy to shape (high-hydration doughs are an exception, as they are difficult to shape).	The dough might be slack due to a lack of gluten development and gas buildup.	The dough feels very wet, slack, or even soupy. Extremely difficult to shape.
The dough smells yeasty.	The dough might smell like flour.	The dough smells acidic and sour.

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What to do if your dough is under or over-proofed?

Sometimes you decide to end bulk fermentation, and when you’re shaping the dough, you notice that something seems off. You might have under or over-proofed your dough!

It’s important to learn how to adjust depending on the bulk fermentation signs above. In most cases, you’ll still end up with a decent loaf of sourdough bread!

If you’ve moved on to pre-shaping or shaping your dough and notice that it is under or over-proofed, there are many different options you can take.

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Under-proofed Dough:

An under-proofed dough is much easier to save than an over-proofed dough. This is because an under-proofed dough simply needs to be proofed longer. If your sourdough is not rising during bulk fermentation at all, you might need to strengthen your sourdough starter.

If you notice the dough is under proofed during preshaping or shaping, simply give it a longer bench rest. By letting the dough rest longer during preshaping or shaping, the bulk fermentation stage is essentially extended.

The dough will continue to proof very slowly in the refrigerator, so you can also extend a cold, overnight proof. Depending on the recipe, you might be able to extend the cold proof for up to a few days.

If the dough still seems under proofed once taken out of the refrigerator, let it proof longer at room temperature before baking.

Here’s an under proofed bread I baked and posted on my Instagram:

View this post on Instagram

A post shared by Sourdough Brandon (@sourdoughbrandon)

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Over-proofed Dough:

An over-proofed dough is more difficult to save than an under-proofed dough.

If the dough is only slightly over-proofed at the end of bulk fermentation, divide and shape the dough into a banneton immediately and place it directly in the refrigerator. The cold temperature will slow down fermentation and your bread will likely end up okay.

A dough that is extremely over-proofed might not be salvageable for sourdough bread. If it’s so wet and slack that you cannot shape the bread, I would advise making focaccia out of it! Dump the dough out onto a sheet pan with a lot of olive oil, dimple it all over, add salt and any toppings and bake at 450ºF for 20-25 minutes.

An example of a slightly over-proofed sourdough below from my Instagram:

View this post on Instagram

A post shared by Sourdough Brandon (@sourdoughbrandon)

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Can You Bulk Ferment in the Refrigerator?

Generally, no. Bulk fermentation is meant to ferment at a warm enough location for the sourdough yeasts to produce carbon dioxide and multiply (ideally between 75-80ºF).

In a cold location like the refrigerator, the yeasts ferment at an extremely slow pace, which hinders bulk fermentation.

However, if you’ve proofed your dough for a few hours in a warm location, you can transfer the dough to the refrigerator for the last couple of hours to finish bulk fermentation.

Essentially, the yeasts have activated enough at this point that they will continue to expand more in the refrigerator.

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Conclusion

Bulk fermentation doesn’t have to be intimidating or as mysterious as it seems.

Most of the process is hands-off; allow the sourdough yeasts to do their job. Another part of it is a baker’s intuition that comes with experience and practice.

Learn the various signs and indicators when bulk fermentation is complete and you’ll be 90% there!

And experiment! Let your dough ferment much longer than normal and see what happens. Or cut bulk fermentation short and see what an under-proofed dough feels like. Those experiments with your dough taken to extremes can help you get to know your dough better and make you a better baker.

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