Sourdough Bulk Fermentation Guide

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Bulk fermentation is the key to achieving a sour, flavorful loaf with a moist, airy crumb. Master the art of bulk fermenting with this guide!

Sourdough is an incredibly intuitive process but it can be difficult to navigate when you’re new or inexperienced. The terms can be unfamiliar and it can be difficult to understand exactly what’s happening behind the scenes.

One of the most important steps in sourdough baking is bulk fermentation. Bulk fermentation is also called first rise or primary fermentation, depending on the baker’s preferred term.

Bulk fermentation allows bakers to develop a strong gluten network easily. This process does not require machine or manual kneading or mixing to create dough strength, only stretch and folds, and time.

This sourdough bulk fermentation guide is dedicated to the perfect loaf.

Baked sourdough in blue dutch oven.

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What Is Bulk Fermentation?

Bulk fermentation starts as soon as all the ingredients are combined and ends when the dough is divided and shaped. This is usually the longest stage of the sourdough process unless you’re cold-proofing in the fridge.

This process is known as bulk fermentation because generally bakers mix and ferment multiple batches of sourdough together in bulk. If you’re a home baker only making 1 loaf at a time, a more apt name might be primary fermentation, that said, the process is the same, regardless of dough volume.

New to sourdough baking? Check out my sourdough bread recipes and guides!

A sliced sourdough cinnamon raisin loaf.

Baking In Bulk

Bulk fermentation has several advantages over smaller batches:

  • predictable fermentation patterns due to the larger mass of dough maintaining a consistent temperature better than smaller batches.
  • you only need to observe a single dough versus several smaller doughs.
  • fewer dirty dishes.
  • allows for long cold-proof in the fridge when batching multiple loaves.
Ripe sourdough starter in a mason jar.

Why Is Bulk Fermentation Important For Sourdough?

During dough bulk fermentation, the microbes in your sourdough starter are hard at work multiplying and creating acids that improve flavor and dough strength as well as C02 gasses which add volume and airiness to your dough.

Both the yeasts and lactobacillus bacteria in the starter work together to create a beautiful end product, but they need time to work, and we need to help them along.

Bulk fermentation is responsible for the development of your sourdough’s tangy flavor, the characteristic open crumb structure and texture, rise, and more. Proper fermentation is vital to a proper loaf of sourdough. Improper management of the bulk ferment can result in under-proofed or over-proofed loaves with undesirable characteristics.

This stage of the baking process also allows for gluten development via the stretch and fold process without requiring intensive kneading or mechanical mixing.

Sliced jalapeno cheddar sourdough bread.

Stretch + Fold

Bulk fermentation is a great way to develop structure and strength in your dough without intensive input. That said, it does require some effort!

That’s where the stretch and fold process comes in. These are quick and simple actions in which you grasp the dough and stretch it out before folding it over itself, then rotate the bowl 90 degrees before repeating, until you’ve gone around the entire bowl. Each set has a profound effect on the texture and development of the dough.

Stretch and folds also perform another, less obvious, but super important function. They help improve the bulk fermentation process by regulating the temperature of the dough – during the process, the cooler dough from the outside is brought inward to ensure consistent fermentation rates throughout.

The last big benefit to stretching and folding sourdough at regular intervals is that we, as bakers, are able to keep a keen eye on the development of our dough.

Dough that has been over-exercised can result in a tight crumb while under-handled dough doesn’t have the strength to hold its shape during baking, resulting in a flat loaf.

Although it seems like alchemy when you’re new to baking sourdough, experience will help guide you and you’ll be able to determine if your dough is ready for shaping or needs more time in the bulk ferment just by handling it.

Stretch + Fold Best Practices

Stretch and folds are best done quickly, and depending on your dough, may be best done with dampened fingers to prevent dough from sticking. After each set, it’s imperative to allow the dough to rest and relax as the dough firms up and becomes taut.

Continuing to manipulate taut dough can result in tears, which is undesirable. If you find the dough too tense to work with, recover it and allow it to rest for another 30 minutes before attempting to try again.

My personal preference is to perform a stretch and fold every 30 minutes over the span of 2 hours. This allows for 3-4 sets of dough manipulation and ample relaxation time for the dough within a 2-hour period.

That said, the timing and number of repetitions can change depending on many factors. But once you become familiar with your starter, your recipes, and your baking environment, you’ll fall into a rhythm.

Factors That Affect Bulk Fermentation

I swear that each and every batch of sourdough is different and there are many things that can affect bulk fermentation and the development of your dough:

  • room temperature
  • temperature of the dough
  • moisture level in the dough
  • quantity of starter in the recipe
  • activity of the starter
  • add ins
Sliced sourdough loaves.

How To Tell If The Bulk Fermentation Is Done?

Time can be a helpful tool during bulk ferment, but the most important measure of bulk fermentation is the development of the bread dough. You can determine the development by looking at and handling the dough.

Properly bulk-fermented sourdough will:

  • have increased in volume
  • look and feel lighter and airier and may have visible gas bubbles
  • be smooth and elastic
  • have a dome-like shape and pull away from the edges of the container
  • not be sticky

Sourdough does NOT need to double during the bulk ferment, look instead to the signs above to gauge dough maturity.

Sounds overwhelming?

Don’t worry, you’ll develop a feel and knack for your dough, the more you work with it, the more confident and comfortable you’ll be at judging the dough during the bulk.

Something Went Wrong?!

If you’ve noticed something gone astray during the bulk ferment, don’t despair. Sourdough is somewhat forgiving and usually, you’ll get a somewhat decent loaf out of it!

There are a few things you can do to salvage your dough depending on the problem

Fixing Under-Proofed Sourdough

Under-proofed dough is distinguished by its lack of growth, stiffness, and lack of elasticity and it may smell more like flour than dough. Fixing this problem is incredibly easy! Extend your bulk ferment until the dough shows signs of maturity.

If you chronically have under-proofed dough, it may be beneficial to examine your baking environment and ingredients.

A weak starter can take too long to activate and result in under-proofed dough. You can fix a weak starter by following good sourdough starter feeding and maintenance practices.

Once shaped, the loaves can be placed in the fridge for a while, to continue proofing. Even though the activity is slowed, it continues to progress.

A cool fermenting environment can cause under-proofing. An easy way to improve the activity of the microbes is to control the temperature and humidity of the proofing environment.

I can easily manipulate the environment in my Brod + Taylor Proofing Box. The photos below illustrate the incredible difference a proofing box can have on your fermentation process. I discuss that experiment in more detail in my Cinnamon Raisin Sourdough Bread post.

Fixing Over-Proofed Dough

Over-proofed dough is a little harder to remedy, but that doesn’t mean it isn’t salvageable. Visually, over-proofed dough will look flatter and less domed and will feel slack and loose.

The easiest fix for barely over-proofed dough is to quickly shape it, place it in a banneton or alternative, cover it, and toss it in the fridge to slow the fermentation process.

A very over-proofed dough will be more difficult to salvage, and baking it may result in a denser, flatter loaf with stronger sour notes. If the dough refuses to hold any shape, transfer it into a greased loaf pan or baking dish and use the rigid structure to create shape for your loaf.

Fresh baked loaves of sourdough.

Notes From The Crave Kitchen

Bulk fermentation is a key step in the sourdough bread baking process and requires patience and skill. Factors such as temperature, moisture level, and starter strength can all affect the development of dough during bulk fermentation. It’s important to familiarize yourself with your ingredients, recipes, and environment so that you can accurately assess the maturity of your dough. With the right knowledge and practice, you will be able to make perfect sourdough loaves every time.

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Sourdough starter jar with text overlay: sourdough 101 bulk fermentation.

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