person holding a sourdough bread

Sourdough bread

Sourdough bread

Sourdough bread is a type of bread that is created by fermenting dough with wild Lactobacillaceae and yeast. Fermentation produces lactic acid, which gives the product a sour flavor and improves the shelf life.


Michael Gaenzle states in the Encyclopedia of Food Microbiology: “Everything claimed regarding the origins of bread-making must be pure speculation because they are so ancient. One of the oldest sourdough loaves was discovered in Switzerland in 3700 BCE, although the origin of sourdough fermentation is most likely linked to the Fertile Crescent and Egypt many thousand years earlier “, which was further supported by archaeological data a few years later. “For most of human history, bread production relied on the use of sourdough as a leavening agent; the use of baker’s yeast as a leavening agent dates back less than 150 years.”

In his Natural History, Pliny the Elder described the sourdough process as follows:

However, they usually do not heat it at all, instead of using leftover dough from the day before; obviously, sourness causes the dough to ferment.

Sourdough was the most common kind of leavening in Europe until it was superseded by barm from the beer brewing process, and then by purpose-cultured yeast after 1871.

Bread made entirely of rye flour, which is common in northern Europe, is frequently leavened with sourdough. Baker’s yeast is ineffective as a leavening agent in rye bread because rye lacks sufficient gluten. The starch in the flour, as well as additional carbohydrates known as pentosans, give rye bread its structure; nevertheless, rye amylase is active at far higher temperatures than wheat amylase, causing the bread’s structure to crumble when the starches are broken down during cooking. As a result, the lower pH of a sourdough starter inactivates amylases in a way that heat cannot, allowing the carbohydrates in the bread to gel and set properly.

In the southern part of Europe, where sourdough is still used to leaven panettone, sourdough has become less common in the twentieth century; it has been replaced by faster-growing baker’s yeast, which is sometimes supplemented with longer fermentation rests to allow for some bacterial activity to build flavor. Although it is usually employed in conjunction with baker’s yeast as a leavening agent, sourdough fermentation has re-emerged as a prominent fermentation technique in bread manufacturing in the last 10 years.

During the California Gold Rush, French bakers brought sourdough skills to Northern California, and it is still a part of San Francisco’s culture today. (The term lives on in the San Francisco 49ers’ mascot, “Sourdough Sam.”) Although the 1849 gold prospectors were more likely to cook bread with commercial yeast or baking soda, sourdough has long been linked with them. The “celebrated” San Francisco sourdough is white bread with a strong sour flavor, and the Lactobacillus strain found in sourdough starters is called Fructilactobacillus sanfranciscensis (formerly Lactobacillus sanfranciscensis), coupled with the sourdough yeast Kasachstania humilis.


During the Klondike Gold Rush of 1898, the sourdough tradition was introduced into Alaska and the Yukon Territories of Canada. In the conditions experienced by the prospectors, traditional leavenings like yeast and baking soda were far less reliable. Experienced miners and other settlers often wore a pouch starting around their necks or on their belts, which they carefully guarded to avoid freezing. Excessive heat, notice, is what kills a sourdough starter. Old hands were dubbed “sourdoughs,” a word that is still used to refer to any Alaskan or Klondike veteran. Robert Service’s writings, particularly his collection of “Songs of a Sourdough,” memorialized the significance of the nickname’s link with Yukon culture.

Sourdough is no longer the standard method for bread leavening in English-speaking countries, where wheat-based bread is the norm. It was gradually phased out, first by the use of barm from beer production, and then, after Louis Pasteur’s validation of germ theory, by cultured yeasts. Despite the fact that sourdough bread was phased out of commercial bakeries in the twentieth century, it has seen a resurgence among artisan bakers and, more recently, industrial bakeries.

Non-sourdough bread manufacturers compensate for the lack of yeast and bacterial culture by incorporating an artificially-made combination known as bread improver or flour improver into their dough.


By putting flour and water into the starter 4 to 12 hours before adding to the dough, the starting must be nourished. This makes an active leaven that will expand in size and be ready to use once it is bubbly and floats in water. To form a final dough of the right consistency, combine the leaven with flour and water. Though recipes may vary, the beginning weight is normally 13 percent to 25% of the overall flour weight. The dough is fashioned into loaves, then allowed to rise before being baked. For sourdough bread, there is a variety of ‘no knead’ procedures. Because sourdough bread takes so long to prove, many bakers will chill their loaves before baking. To slow down the proofing process, this is known as’retardation.’ This method also results in a loaf with a more complex flavor.

Sourdough starters are often inappropriate for use in a bread machine since their rise time is longer than that of bread made using baker’s yeasts. However, sourdough that has been proved for several hours using a sourdough starter or mother dough can be transferred to the machine, eliminating the timed mechanical kneading by the machine’s paddle and using only the baking part of the bread-making procedure. Although this is efficient for single-loaf production, the complex blistered and slashed crust qualities of oven-baked sourdough bread cannot be achieved in a bread-making machine, as this usually necessitates the use of a baking stone in the oven and steam misting of the dough. Furthermore, perfect crust development necessitates loaves with shapes that are impossible to achieve in a machine’s loaf pan.


Types of bread

Many pieces of bread are made with procedures comparable to those used to make sourdough bread. Danish rugbrd (rye bread) is a dense, dark bread that is most known for being used in Danish smrrebrd (open-faced sandwiches). The Mexican birote Salado originated in Guadalajara as a short French baguette that uses a sourdough fermentation process instead of yeast, resulting in a bread that is crispy on the exterior yet soft and savory on the inside.

A sourdough starter with sugar and milk is used to make Amish friendship bread. Baking powder and baking soda are also used to leaven the dough. Every 3–5 days, an Amish sourdough is given sugar and potato flakes. Modern pumpernickel loaves are typically laced with citric acid or lactic acid to inactivate the amylases in the rye flour, whereas classic pumpernickel loaves are traditionally baked with a sourdough starter. A whole-wheat sourdough, Flemish desem bread (the name means starter). Whole-wheat sourdough flatbreads are historically consumed in Azerbaijan. Teff flour is fermented to make injera in Ethiopia. Somalia, Djibouti, and Yemen eat a similar version (where it is known as lah oh). Idlis and dosa are rice and Vigna mungo sourdough fermented bread in India.

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