Baking School Day 14: Sourdough Breads

updated May 1, 2019
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(Image credit: Lindsay Ribe)

The Kitchn’s Baking School Day 14: All about sourdough breads.
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Different from most other breads that start with commercially packaged yeast, sourdough bread uses naturally occurring bacteria and yeast in the environment. This wild yeast creates a bread with superior texture and complex flavor — sometimes mildly sour from the bacteria or lactobacilli captured in the starters.

Whoa, hold on there! You thought sourdough was all about bread bowls and San Francisco, so what’s with all the scientific names and procedures? Don’t worry, we will get there, and it will be totally worth it!

Sourdough bread with cheese baked inside. (Image credit: Melissa Ryan)
(Image credit: Lindsay Ribe)

What Is Wild Yeast?

As discussed briefly earlier this week, wild yeast is the key to making sourdough starter. Yeast is airborne and it also lives on the surface of things like grapes and flour; it is in the environment all around us. While commercial yeast is mass-produced and packaged, wild yeast must be captured and cultivated before heading into a bread recipe. Wild yeast can feel high-maintenance; when making one from scratch, it must be cared for, nourished, and fed for nearly the course of a week before it’s ready. However, once you have the culture made, it’s easy to keep it going, and if carefully managed, it can last indefinitely!

What Is a Sourdough Starter?

Captured yeast and lactobacilli in a mixture of water and flour will become your sourdough starter. The starter develops as it is fed and the wild yeast multiplies. After this mixture has been ripened and cared for, it’s added to the remaining ingredients to create a loaf (or two) of bread.

Get Your Step-by-Step Baking Lesson:
How To Make Your Own Sourdough Starter

Because a sourdough starter relies on the wild yeast in flour and air around us, starters from around the world will taste different. The strain of yeast and lactic acid from the bacteria of each region gives starters their own unique flavor.

How to Make Sourdough Starter

If you were not fortunate enough to inherit an heirloom starter that’s been cultivating for years, you can start your own!

The whole process takes about five days. On day one, equal parts flour and filtered water are combined together into a smooth paste in a tall glass or plastic container. Cover the container loosely with plastic and leave it to begin culturing wild yeast. A cool 70°F to 75°F room is best.

Each day, more yeast and bacteria will develop, which will feed on the sugars in the flour and release carbon dioxide. To keep things going, add more flour and water to “feed” your growing starter. Stir until smooth and leave the starter again to continue to grow.

As the week progresses, the starter should begin to appear bubbly (caused by the carbon dioxide being released from working yeast) and start to smell sour. Continue to feed and rest at 70°F to 75°F.

By day five, the starter should be very bubbly and frothy and smell sharp and tangy. If so, your starter is ripe and ready to go!

Get Your Step-by-Step Baking Lesson:
How To Make Sourdough Bread

(Image credit: Melissa Ryan)

Other Pre-Ferments

Many artisan bread doughs are made using something that’s in between the straight yeast of a loaf of sandwich bread and the sourdough culture for making sourdough bread — they are made with something called a pre-ferment. Also known as a sponge, biga, or starter, this is just a small mix of flour, water, and commercial yeast (no wild yeast) that is made in advance of making the bread itself. The pre-ferment is left to ferment for a few hours or overnight, and then it gets mixed into the main dough, along with the rest of the ingredients.

Using a pre-ferment means a longer, slower bread-making process, but the result is a more flavorful, softer bread with a thicker, chewier crust and superior texture. Using a pre-ferment is a good way to ease into making artisan bread without the commitment of a five-day sourdough starter.

Your Vocabulary Lesson of the Day

  • Poolish: A French bread starter using the sponge method. It is very soft and batter-like.
  • Biga: An Italian bread starter that has a high ratio of flour that makes it more similar to a dough.
  • Levain: The French form of a sourdough starter.
  • Barm: The English form of a sourdough starter.
The dough during the autolyse stage. (Image credit: Emma Christensen)

What Is Autolyse?

Autolyse is the resting period that takes place after the dough is mixed, but before it is kneaded. It combines the remaining ingredients (although sometimes salt is added after) and allows the flour to hydrate and the gluten to start to develop. This rest gives the flour an opportunity to absorb the maximum amount of water.

Some Tips on Shaping Bread

Once the dough ferments and rises, turn it out onto a lightly floured surface. Sourdough bread usually isn’t punched down like regular bread; instead, handle it gently to avoid deflating or collapsing the gluten structure.

Portion out your dough, and then let it rest before shaping it into loaves. This resting period gives the gluten time to relax and makes it easier to stretch and shape the dough. Use only as much flour as needed to keep the dough from sticking as you shape it.

Boules or Round Loaves

Gather and tuck in the ends of the dough towards the center. Holding it in your hands, rotate the dough and keep tucking until the ball becomes tight with a smooth skin. To further tighten the skin, place the dough on your work surface and begin rotating it around between the palms of your hands.


Use a bench cutter to divide the dough — usually three or four equal pieces. Smooth-side down, pat the dough down and shape into rectangles — about 10 inches by 8 inches. Like a business letter, fold the dough into thirds, folding the top third down and the bottom third up towards the center. Seal the bread by using the palm of your hand to knock out any air bubbles and form a tight skin. Fold the dough in half and seal again. Starting with the middle of the dough and working out towards the ends, use a soft hand to roll the dough into a long baguette shape — about 12 to 15 inches in length.


Starting like the baguette, shape a batard so it tapers off at the ends, but keeps a bit of volume in the center.

Get Your Step-by-Step Baking Lesson:
How To Make Ciabatta Rolls and Bread at Home

(Image credit: Emma Christensen)

What Proofing Baskets Do for Your Bread

Proofing baskets are usually made of wicker or coiled rattan and are used to keep the shape of dough during its final rise. They are available in all sizes and shapes to hold your boules and baguettes.

To use them, dust thoroughly with flour and then tip the shaped loaf inside, seam-side up. You can also line the forms with canvas and then flour them, if you prefer. The basket supports the dough as it relaxes and keeps it from flattening out during this last rise. When ready to bake, invert the dough back onto a baking peel.

Why (and How) to Slash Your Bread Loaf

The patterns that appear on top of artisanal breads are not just ornamental: Beyond making an attractive loaf of bread, the slashes open up the structure and alleviate the pressure that builds up during baking. Slashing the top of dough before it bakes allows it to rise properly. Since bread rises so rapidly during baking, an un-cut dough may crack at the weak points. By having the chance to cut the dough beforehand, you are predetermining where the bread will “crack,” making sure it is done uniformly for more even baking.

Slash the bread with a small serrated knife, sharp razor blade, or “lame” just under the surface of the skin and at a slight angle; take care to cut and not snag the dough.

Baking Bread: The Basics

Before baking off your beautiful loaf of bread, make sure the oven is completely preheated to the correct temperature. If you are using a baking stone or equivalent, be sure to place it in the oven while it is still cold, or per instructions in your recipe.

Professional bakers use a “peel” to shuffle loaves into and out of the ovens. This is similar to a pizza peel, but with a much longer handle. Home bakers can use peels, too! Using one helps make moving a loaf of dough onto and off of a baking stone much easier. Many homemade artisan breads can also be baked inside a Dutch oven.

The Role of Humidity During Baking

To create a superior crust, it is important to keep the oven moist. During the first eight minutes of baking, the gases in the dough will rapidly expand while the water content turns into steam. The steam and the expanding gas inflate the dough and give the bread its final rise. The yeast have one final splurge before they are killed off from the heat of the oven. This burst of activity is also know as “ovenspring.”

The humidity in the oven will prevent the crust from forming too early, allowing the bread to rise to its fullest potential during this time. The humidity in the oven will also yield a thicker, crisper crust that is glossy and beautifully browned in the end.

To achieve this humid environment, you can use a mister or a water bath. Place a baking pan in the bottom of the oven as it preheats. When you put the dough in the oven, toss in a few ice cubes or a cup of hot water that will evaporate into steam. Spritzing the inside of the oven intermittently in the first few minutes also works, but be careful not to let too much heat out.

Another easy trick is to have the bread use its own steam that is being produced as it bakes. Trap the stream by baking the bread in a covered Dutch oven or cloche for the same effect. You may also use a large metal bowl or any other oven-safe baking dish or lid to cover, just as long as they are deep enough and allow the bread to rise freely.

It should be noted that the oven should only be kept humid during the first 10 minutes or so of baking; after the dough begins to set, the crust will need to dry out.

Delicious sourdough bread — made at home! (Image credit: Emma Christensen)
(Image credit: Lindsay Ribe)

Every lesson has three homework options. Maybe you’ve already got one down, or you just have time for a quick study session. So pick one, and show us by tagging it with #kitchnbakingschool on Instagram or Twitter.

(Image credit: Lindsay Ribe)

Go buy some sourdough bread and have it with dinner tonight.

(Image credit: Lindsay Ribe)

Start your own sourdough starter.

(Image credit: Lindsay Ribe)

Make a loaf of bread with poolish, or make a loaf of sourdough.

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