The Science of Sourdough Bread... and Butter

About a year ago I started making naturally leavened, also known as sourdough bread. This amazing bread requires a starter, which contains natural yeast and beneficial bacteria. The dough is wet and sticky, and handling it takes some practice. Also, it takes much longer to make compared to bread made with baker's yeast. In this day and age of instant gratification, commercially produced, chemically-enhanced, fortified white bread, I want to show you a better way, a natural way.

While learning to make this bread, I discovered sourdough's many health benefits and it seemed only natural to use the least processed ingredients I could find. I use only certified organic flour, which I buy from a small, but fabulous company called Great River Organic Milling in Wisconsin. If you truly want to make phenomenal bread I encourage you to check them out. Their products are also available on Amazon.

Scientists theorize that bread has been with us for 30,000 years, although the first written record of bread appeared 6000 years ago. It is thought that bread was responsible for mankind's leap from hunter-gatherers to an agricultural society.

Let’s Talk Science: The process of making bread is all about fermentation. Most grain is indigestible unless it has been fermented. The microorganisms required for fermentation are already on the grain and in our environment. All you have to do is grind the grain into flour, add water, mix and let the mixture sit until large colonies of yeast and bacteria grow. As these microorganisms use the nutrients of the grain as a food source, CO2 and alcohol are produced. This process is called fermentation. After fermentation the only thing left is to apply heat and there you have it. BREAD! It truly is a miracle of our species.

During fermentation of the dough, several things happen that make this bread healthier. Components in the flour are broken down making vitamins and minerals available for absorption. Also, gluten is broken down to a more digestible form. Any bread produced with baker’s yeast, whether made at home or commercially produced, takes only a couple hours to make and does not have the same nutritional value as fermented bread. That is the reason commercially produced breads are fortified with vitamins. Even commercially produced sourdough is most likely flavored and not actually naturally leavened bread.

Now, let's make some bread!

Step 1: Creating the Sourdough Starter or Leaven

Sourdough starter is nothing more than equal amounts of flour and water by weight, mixed together and left at room temperature for a few days. It takes 15-30 days before the population of yeast and bacteria in the starter is large enough to make bread. We're talking 50 million yeast and 5 billion bacteria per teaspoon of starter. Feed the starter one to two times a day by discarding a portion then add more flour and water in equal amounts by weight.

Since natural yeast is on the grain, I mill my own flour to make a starter. However, you can use any kind of flour. In fact, once my starter is strong and active, I switch to using organic all-purpose flour. Also, starters from all over the world may be purchased online to make many styles of bread.

The bacteria in the starter, called lactobacilli, produces lactic acid and acetic acid which act as a natural preservatives and gives sourdough its distinctive flavor.

If the starter is left at room temperature, it must be fed one to two times a day. Or the starter can be refrigerated for up to two weeks between feedings. I pull my starter out of the refrigerator a day or two before I make bread and allow it to come to room temperature, then feed it a few times to freshen it up.

Equipment: 1 quart canning jars with lids, cheese cloth, a rubber spatula small enough to fit in the jar and stir the ingredients, a canning funnel can be helpful but isn't essential and containers for measuring flour and water, a scale which can weigh up to 5-6 kilograms or 11-12 pounds

Helpful Hints: Do not use chlorinated water for your starter or your bread. I use drinking water that I purchase from the water store. Keep the top of the canning jar, inside and out, meticulously clean. When the starter dries it's like glue. If the cheese cloth comes in contact with the starter you'll tear holes in it trying to get it un-stuck.

Step 2: Preparing to Make the Dough

I weigh out all the ingredients the night before, then six to eight hours before making bread, I take a portion of the active starter, equal amounts of flour and water, mix them in a bowl, and cover. This is called a "poolish" in some circles. It is essentially another starter that you can use to make the bread. The amount of poolish needed depends on how much bread will be made. See recipe below.

The proportion of bacteria to yeast in the starter determines how sour the bread will be. Discarding less of the starter when feeding and/or feeding less often promotes a larger population of bacteria. Also, if you use the starter rather than making a poolish, or use larger amounts of starter per batch, your bread will be more sour. I discard most of the starter when feeding, which makes it less sour.

The poolish or starter should be at its peak of activity when used to make bread. It will be full of bubbles and will float in water when ready.

This is the recipe for my Multi Grain Bread (makes 3 one kilogram loaves):

Bread flour................................1400 grams

Whole wheat bread flour.............400 grams

Seven grain flour.........................100 grams

Sunflower Millet Flour Blend.......120 grams

Poolish........................................200 grams

Water.........................................1670 grams plus 50 grams.....85% (Bakers Percentage)

Salt................................................44 grams...............................2% (Bakers Percentage)

I use a system called Bakers Percentages to determine the amount of water and salt to use for each recipe. Sourdough is generally a 70-85% hydration. This is calculated by adding up the total weight of dry flour and multiplying it by the percentage desired. The poolish doesn't count because it is a 1:1 ratio of flour to water or 100% hydration. For the formula above, the total weight of dry flour is 2020 grams. 2020 X .85 = 1717 grams of water. I round up to 1720 grams.

For the salt I add up the total amount of dry flour as well as the poolish. 2% salt is the standard for most bread making. 2220 X .02 = 44.4 grams of salt rounded to 44 grams.

Step 3: Making the Dough

With all ingredients weighed out and the poolish or starter ready to go, it's time to make the dough. I use an 8 quart stainless steel bowl for mixing. First, I add 1670 grams of the water and 200 grams of the poolish to the bowl, then stir until the starter has mostly dissolved. Then I add all the flour and mix with a rubber spatula until the dough comes together. I finish mixing using a wire dough whisk until there is no dry flour and all lumps have disappeared. Then I place the dough into a food grade plastic bucket with a tight fitting lid and let the dough rest for 40 minutes.

This rest period, called autolyse, allows the flour to absorb the maximum amount of water. Enzymes that break down starch into simple sugars are activated and gluten begins to form.

Helpful Hints: Natural yeast works best at around 80 degrees Fahrenheit. Depending on the temperature of my kitchen, I will often warm the water before mixing the dough. If my kitchen is 70 degrees, I'll warm the water to about 90 degrees. After mixing, the dough will be very close to 80 degrees. This helps jump start the yeast.

Step 4: Adding the Salt

Add the salt and the remaining 50 grams of water when the autolyse period is complete. Do this by evenly sprinkling the salt over the top of the dough, then add the water. Incorporate the salt into the dough by poking holes from top to bottom in several places, as well as along the side of the bucket. Once most of the salty water has been incorporated into the dough, it's time to start kneading.

Knead the dough by reaching down the side of the bucket with a wet hand, grab the bottom of the dough, stretch it up and fold it over onto itself. Turn the bucket a quarter of a turn and repeat. Do this for 3-5 minutes. (See video).

Helpful Hints: Don't worry if the dough falls apart after adding the water. Just keep kneading and it will come back together.

Step 5: Kneading and Proofing the Dough

Kneading the dough develops gluten strands. The gluten forms an elastic mesh throughout the dough that traps the CO2 produced during fermentation, creating thousands of bubbles. This makes the dough rise and gives bread its structure and texture.

Knead the dough every 30 minutes for the next 5-6 hours. As the dough develops and begins to rise, knead less aggressively to avoid tearing the gluten strands and deflating the dough. Also, each time the dough is kneaded, you will feel it stiffen and become firmer. This is when the dough should be grabbed from the top rather than from the bottom of the bucket, stretched to the other side and held in place for a few seconds. If it isn't held in place it will spring back to its original location.

"Proofing" is a term for letting the dough rise. With this bucket method, you are kneading and proofing at the same time.

Kneading and proofing times are dictated by the starter. At 75-80⁰ F., my starter takes about 6 hours to reach peak activity. It stays active for about an hour, then starts to go dormant as its food supply dwindles. From start to finish, I get my loaves into the oven within 6-8 hours. A good point of reference for this is the starter. Feed your starter as soon as the dough is mixed. Just as the starter becomes very active and doubles in size, it will be time to divide the dough into loaves.

Helpful Hint: An overly long proofing period breaks down too much of the gluten and the bread won't rise.

Step 6: Bench Rest

When the dough has come close to doubling in size, it's time to divide it into loaves. You can divide by eye or by weight for a more consistent loaf. The weights don't have to be exact, just close.

Kneading the dough one last time helps release it from the sides of the bucket. Lay the bucket on its side. When most of the dough has released from the top side, gently lift the bucket, turn it upside down and tilt it to release the rest of the dough.

Divide into loaves, and using a bench scraper form each loaf into an even round. Sprinkle loaves lightly with flour and cover with a clean towel. Let them rest for thirty minutes.

This is called a "bench rest." During this time, the dough continues to proof and a skin begins to develop on the top of the loaf. When the dough is folded and the loaves are shaped, this skin creates an internal structure which helps maintain the shape of the loaf during the final proofing and baking.

Step 7: Folding and Shaping the Loaves

In the video I show a couple different ways to fold and shape the loaves. The process starts immediately after the thirty minute bench rest and is done one to three times at 15 minute intervals. Begin by lightly flouring the top of the loaf, then use a bench scraper to turn it upside down. Make the folds, ending with the loaf right side up. Lastly, use the bench scraper to push the loaf along the work surface from several different directions to stretch and firm up the sides. Cover with a towel and repeat with each loaf.

After shaping, the loaves are placed in baskets for the final proofing. I use ratan baskets, but towel lined bowls work just as well. Generously flour the baskets or towels, if using towel lined bowls, before placing the loaves, upside down, into them. Allow the loaves to proof in the baskets for 30-45 minutes.

Step 8: Preparing to Bake the Loaves

The first 20 minutes of baking the loaves are critical. Steam is necessary to keep the outside of the loaves pliable and to super heat the air that causes the loaves to spring up. This is termed "oven spring" and, for the home baker, is produced by cooking the loaves in lidded pots. I prefer a cast iron combo cooker.

Place the pots in the oven and preheat to 490 ⁰ F. Allow 30-40 minutes for the pots to heat up. Using parchment paper will make it easier to transfer the loaves from the baskets to the pots.

First, turn the loaf out of the basket and onto the parchement paper. Next, score the top of the loaves with a sharp knife or razor. The razor used by bakers is called a "lame." Scoring the loaves will help with oven spring. Remove the bottom part of the pot from the oven and place it on the burner closest to you. Using the parchment paper, place the loaf into the pot. Immediately place the lid on the pot and put into the oven. Repeat with the remaining loaves.

After 20 minutes, the loaves should be doubled in height and lightly browned on top. The top of each loaf should be firm enough to support its own weight when turned out of the pot. If the loaf flattens, the cooking time inside the pot needs to be increased.

Helpful Hints: To preserve heat, keep the oven door closed as much as possible. Close the door immediately after removing or placing something into the oven.

Step 9: Finish Baking the Loaves.

After 20 minutes, reduce the oven temperature to 475 ⁰ F, remove the loaves from the pots and place on parchment lined baking sheets. Return the loaves to the oven and bake for 15-20 minutes or until the loaves are a rich brown color. Remove the bread from the oven, place on a cooling rack and let cool for 2 hours. The bread can be stored in plastic bags which will soften the crust or left out a crispy crunchy crust. By the way, this bread makes excellent toast!

Step 10: What's Bread Without Butter?

With a food processor, using a spiral blade at high speed, butter can be made in about 30 minutes. In the photos you can see the process of cream changing to whipped cream, then changing color, then getting grainy and turning yellow, then all of a sudden BUTTER!

Once the cream separates into butter and buttermilk, which takes 15-18 minutes, pour off the buttermilk and place the clumps of butter in a large mixing bowl. Add very cold water (non-chlorinated, refrigerated) and knead the butter to remove more of the buttermilk. When the water turns cloudy pour it out. Repeat 2-3 times or until the water remains clear. The more buttermilk that is removed, the longer the butter will keep.

Once rinsed, add salt to taste, mix, and the butter is ready to slather onto your freshly baked, naturally leavened and healthy bread!

Enjoy, you deserve it!

Step 11: References

At this point I would like to mention the book that got me started, Tartine Bread by Chad Robertson. This is a wonderful book written exclusively for those wanting to make sourdough bread at home.

Forkish, K. (2012). Flour Water Salt Yeast. Berkeley: Ten Speed Press.

Hamelman, J. (2013). Bread. Hoboken: John Wiley & Sons, Inc.

Reinhart, P. (2016). The Bread Baker's Apprentice. Berkeley: Ten Speed Press.

Robertson, C. (2010). Tartine Bread. San Francisco: Chronicle Books.

Wood, E. W. (2011). Classic Sourdoughs. Berkeley: Ten Speed Press.