If you’ve ever had store-bought sourdough bread, you’re probably used to a very particular flavor: tangy, pungent, in a word… sour. While this kind of San Francisco sourdough is famous for its bite, sourdough bread can taste as mild as a simple loaf of pain au levain. The wide range of flavors comes from the fact that “sourdough” doesn’t refer to a particular style of loaf so much as a way of leavening it. While modern store-bought loaves of bread are made with single species of commercial yeast, S. cerevisiae, sourdough breads rely on a process called lacto-fermentation to create a crisp, flavorful loaf.
To really understand what makes sourdough bread special, let’s take a quick look at the regular stuff: baked goods made with commercial yeast. Called baker’s yeast, brewer’s yeast, instant dry yeast, or active dry yeast, strains of S. cerevisiae are in all kinds of foods. Fermenting everything from wine to doughnuts, commercial yeast is convenient, predictable, and simple to use. Dry yeast can be stored at room temperature for months, making it easy to bake whenever the spirit moves ya. After adding water, the yeast instantly starts to grow and multiply. And because all commercial yeast belongs to the same species, we can take a pretty good guess about how it’s going to act in a dough.
With so many good reasons to use commercial yeast, why go to the trouble of messing with sourdough? It can taken a dozen more hours to rise, requires weekly maintenance, and can sometimes leave you with disappointing results. But when it works – and that is often! – making sourdough satisfies your palate, gut, and ego.
To make sourdough bread, we don’t add any yeast to our dough. Instead, we grow it. Wild yeast exists everywhere: on plants, in our bodies, and in the air. They’re tiny, single-celled fungi that thrive in wet, temperate conditions. If we want to make sourdough, we alter the environment of a little jar of water and flour so that the wild yeast starts to reproduce. Once we have grown a nice, strong colony of yeasts, we introduce them to dough. Yeast eats starch and gives off alcohol and carbon dioxide, causing the dough to rise.
But yeast is only half of what makes sourdough special. The other half, lacto-bacteria, exists in harmony with the yeast. When lacto-bacteria eats starch, it gives off lactic acid. The lactic acid produced leads to all kinds of great flavors; fermented foods like dosas, lambics, kombucha, and injera all share similar sour, delicious qualities. Sourdough also lasts longer than regular bread. Lactic acid inhibits the growth of harmful bacteria and molds, naturally preserving your homemade loaf of sourdough bread.
Together, the yeast and bacteria reactions are called “Lacto-fermentation.”
Lots of sourdough bakers and scientists believe that lacto-fermented bread is more nutritious for us than commercially leavened breads. Sourdough breads tend to have lower glycemic indexes and more absorbable vitamins and minerals. Lacto-fermented foods can act as probiotics, introducing a healthy mix of bacteria to your gut. For people who have trouble digesting bread, the presences of helpful bacteria may make sourdough breads easier on your system.
Most of all though, making sourdough bread is just plain fun.
When you make sourdough, you’re tapping into a process that has been used by your ancestors – regardless of where in the world they’re from – for millennia. Sourdough is so ancient that no one really knows how it began; the oldest sourdough loaf was discovered in Switzerland and is 5700 years old.
Making and eating sourdough is a whole new way of experiencing your environment. Because you’re harvesting the wild yeast in your home and flour, eating homemade sourdough is tasting the microflora your home. Gross? I don’t think so!
Angelo reserved his most enthusiastic praise for my bread, which I’ll admit did have a perfect crust, an airy crumb, and a very distinctive flavor–the specific flavor, I guess, of the neighborhood yeast
— the omnivore’s dilemma
Creating a sourdough starter and loaf is also the ultimate mindful exercise. Rooted in Buddhist meditation traditions, mindfulness – nonjudgmental observation of the present moment – has been shown to decrease anxiety and stress, heal depression, and help people recovering from substance abuse. Growing your starter, you can focus on how the mixture looks, smells, tastes, and feels rather than wishing the process would hurry up. When you make dough, experiencing the tactile experience of kneading and folding and savoring taste of your final loaf can be grounding. Treat your sourdough starter like you would a houseplant; let it help you tune into the season, heat, humidity of your environment. Is there a better better way to do something or are you comfortable with where you are? Whose day can you make better by sharing a cup of starter or a loaf of bread?
Over the next week, we’ll grow a sourdough starter together and use it to bake your first two leaves of bread over the weekend. All you’ll need is flour, water, and salt and a few tools to bake.
- The Kitchn
- King Arthur Flour
- Sourdough Library
- The Perfect Loaf – Blog
- Wild Yeast – Blog
- The Fresh Loaf – Forum
- Wild Fermentation by Sandor Ellix Katz
- Tartine Bread by Chad Robertson
- Cooked by Michael Pollan – Part III: Air
- On Food and Cooking: The Science and Lore of the Kitchen by Harold McGee – Chapter 10