The first loaf of yeast bread may have arisen as a happy accident. Wild yeast, which is ever-present in the environment, got mixed into a batch of flatbread dough and went to work. The adventurous—or very hungry—baker tried the strangely puffed product and was intrigued by the light texture and touch of sweetness. A taste for yeast bread was born.
At some point, ancient bakers also learned that they could reserve some of the batter or dough from one batch of bread to start the next one. The chewy texture and tangy taste may have taken some getting used to, but today, fans of sourdough bread—a name acquired only in the 1800s—are glad their ancestors made the effort.
Taming the Wild Yeast It’s still possible to “capture” local yeasts with an inviting, kneaded paste of flour and water set on the counter. For more predictable results, you can buy dried packets, similar to other yeast, from natural-food stores or artisan bakeries, which make specialty or ethnic breads.
Any yeast will sour dough if left long enough, but those chosen to make sourdough bread are known for producing tasty results. They belong to a variety called Saccharomyces exiguus (sak-uh-roe-MY-seez EGG-zih-jus)—roughly translated “little sugar mold.” Unlike standard bakers’ yeast, which is grown specifically for rapid rising and consistent taste and texture, these strains are more individualized. While their domesticated cousin is given just a few hours to leaven bread, these yeasts are nurtured for days to stamp the loaf with their particular flavors.
A Little Help from Their FriendsSaccharomyces exiguus can’t take all the credit for the intense flavor and springy consistency that sourdough lovers crave. They work in tandem with a common, “friendly” bacteria called Lactobacillus (lak-toe-buh-SILL-us). Lactobacillus too comes in several strains, which also helps vary the flavors of different sourdough recipes. (The one responsible for making San Francisco’s famous version is aptly named Lactobacillus sanfrancisco.) The partnership works out well for humans and microorganisms alike, as described here:
The risen dough, now called a sponge or starter, is ready for the rest of the bread-making process. It’s kneaded with more flour, allowed to rise again, shaped, and baked. A small amount is held out to begin the life cycle, and loaf making, anew.
Skilled sourdough bakers’ know how long to let fermentation continue, by the sight, smell, and feel of the sponge. This is important, since too much acid breaks down the gluten. Without this protein framework to trap the air, the bread will literally fall flat. Properly cared for, a starter can give rise to many generations of loaves. One San Francisco bakery is making bread from a starter “born” in 1849.
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