Deceptively Simple Sourdough

Photo from Getty Images/Enzo Nguyen@Tercer Ojo Photography

Wild yeast populations exist just about everywhere, from whitish blooms on grapes to a subtle presence on grains. Because they vary greatly from region to region, yeasts give local foods a custom taste. That’s why sourdough bread from San Francisco is justifiably famous; its flavor results from the area’s unique combination of indigenous wild yeast and lactobacillus strains. But guess what? You can make your own fantastic sourdough bread at home, with the yeast and bacteria already present in your kitchen! To me, this is the essence of local food: You’re using ingredients literally unavailable anywhere else.

What is a Sourdough Starter?

Different types of storage leavens all go by varying names: the French levain, the Flemish desem, the English barm, or the more general term sourdough or sourdough starter. Each of these leavens is cultivated, stored, and used in slightly different ways, but all serve the same purpose: They leaven and flavor the bread that’s made from them. Each starter is cultivated over a period of days in a container, relying on wild, rather than commercial, yeast to populate it. Then, the starter is stored in the refrigerator to continue fermenting, and periodically is refreshed or fed.

Sourdough starter is basically a melting pot that allows for a symbiotic interaction between Candida milleri, a yeast fungus present in sourdough cultures, and lactic bacteria, such as Lactobacillus sanfranciscensis. You probably know that yeasts consume sugars during fermentation; bacteria do, too. They don’t compete for sugars, however; lactobacilli eat maltose, which isn’t metabolized by C. milleri. Enzymes and lactobacillus release glucose and fructose sugars from the starch that are metabolized by C. milleri and other yeast strains present. All this results in the amorphous culture you see in the container in your fridge.

Lactobacillus photo from Adobe Stock/Kateryna_Kon 

Once your starter is ready for use, it’s added to bread dough and helps the dough rise before it’s baked. Wild yeast (Saccharomyces exiguous), of which thousands of strains exist, reproduces at a slower rate than commercial yeast (S. cerevisiae), so dough takes longer to rise. Slowing down the fermentation results in more flavor, because it encourages growth of the acid-producing lactobacillus bacteria, which are responsible for the flavor profile of sourdough-based breads.

To a point, this acid production is a good thing. However, the acidification that results from long fermentation can eventually kill the yeasts and break down the gluten in the starter. That’s why it’s critical to regularly refresh the starter; the addition of flour “dilutes” the starter’s acid load, preventing it from becoming too acidic.

Cultivate Your Own Sourdough Starter

To make a sourdough starter, you’ll need flour and water. That’s all. The wild yeasts and lactobacillus bacteria that populate a healthy sourdough starter are already on your grains. You don’t need to add sugar or honey to “feed” the yeast; the grains have plenty of carbs to keep them happily procreating. Also, don’t add salt; it inhibits fermentation, which defeats the purpose of cultivating a starter.

The time it takes to get a starter going varies depending on the room temperature, the type of flour used, and the consistency of the culture. Generally speaking, your starter will be active and ready to use within 3 to 7 days. My starter has been going since late 2009, and I’ve given away lots of it at demonstrations and as gifts. The flour and water provide a homey environment for microscopic yeasts and bacteria.

Fermentation may seem to have an element of magic or alchemy, but it’s actually an easy process! Here are a few tips to get you started:

• Use a container made of glass, stainless steel, or plastic to house your starter. Avoid aluminum, as it reacts with the starter’s acidity. Starter increases in volume as it ferments, so make sure the container is large enough to allow for expansion.
• Use spring water, if possible; bottled is fine. Avoid chlorinated or distilled water.
• Activate your starter with organic, unbleached flour. Once it’s active, organic ingredients are a matter of choice.
• Add a little rye flour on the first day; it ferments quickly and adds enzymes and minerals that help kick-start a new culture.
• Put a lid on your starter container. You don’t need cheesecloth or anything porous between the lid and starter; the yeast and bacteria are already present.
• The ingredient measurements aren’t critical. It’s easier when doing this for the first time to have the parameters defined, but don’t worry about being exact. The main thing is to keep the flour well-hydrated.
• Once your starter is active and bubbly, keep it in the fridge! At warmer temperatures, the starter will ferment much more quickly, requiring frequent refreshment in order to avoid excessive acid buildup. The cool temperature in your refrigerator won’t kill the yeasts, I promise; fermentation will simply proceed at a more leisurely pace.

Photo from Adobe Stock/Julia Sedaeva

Refreshing Your Starter

I usually bake sourdough bread once a week, and it’s convenient to refresh the starter at the same time. I care more about the consistency than the amount of flour and water I add, aiming for just enough water to moisten the flour. I keep my starter fairly stiff; this, along with refrigeration, slows down the fermentation so I don’t have to refresh it more frequently. The converse is also true: The thinner the mixture, the faster it ferments.

I only use a small amount of flour and water to refresh my starter, since I keep a fairly small amount of it going in the fridge. By weight, I use about twice the amount of flour as water. In other words, a typical refreshment would be about 50 grams of water and 100 grams of flour. Some flours absorb more water than others, so if it seems too dry, add a little water. If it seems too wet, add a little flour.

The Flavor of Sourdough

Much of the mass-produced “sourdough” bread available is made with commercial yeast, not sourdough starter. So, what makes sourdough bread sour, if not sourdough starter? The answer is commercially available “sourdough flavors,” which usually contain citric acid, or a blend that includes tartaric or malic acids. If you’re curious, or just don’t feel like bothering with sourdough starter at this point, go ahead and try it!

Try your hand at making sourdough with this Basic Sourdough Boule Recipe. 

Victoria Redhed Miller is the author of From No-Knead to Sourdough: A Simpler Approach to Handmade Bread, the award-winning Craft Distilling, and Pure Poultry. Victoria is also a regular speaker at the Mother Earth News Fair. She lives on an off-grid farm in northwest Washington.