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Sourdough
 

Sourdough is a symbiotic culture of lactobacilli and yeasts used to leaven bread. Sourdough bread has a distinctive taste, due mainly to the lactic acid and acetic acid produced by the lactobacilli.

Sourdough bread is made by using a small amount (20-25%) of "starter" dough, which has the yeast culture, and mixing it with new flour and water. Part of this resulting dough is then saved to use as the starter next time. It is not uncommon to have a baker's starter dough that has had years of history, from many hundreds of previous batches.

Biology and chemistry of sourdough

A sourdough starter is a stable symbiotic culture of yeast and lactobacteria, including the well known Candida milleri (yeast) and Lactobacillus sanfranciscensis (bacteria) of San Francisco sourdough, growing in a paste of flour and water.

A fresh culture begins with a mixture of flour and water. Fresh flour naturally contains a wide variety of yeast and bacteria spores. When wheat flour contacts water, naturally-occurring amylase enzymes break down the starch into complex sugars (saccharose and maltose); maltase converts the sugars into glucose and fructose that yeast can metabolize. The lactobacteria feeds mostly on the metabolism products from the yeast. Rosada, Didier (1997) Advanced Sourdough. Minneapolis: National Baking Center. The mixture develops a balanced, symbotic culture after repeated feedings.

The flour-water mixture can also be inoculated from a previously kept culture. The culture is stable due to its ability to prevent colonization by other yeasts and bacteria as a result of its acidity and other anti-bacterial agents. As a result, many sourdough bread varieties tend to be relatively resistant to spoilage and mold.

The yeast and bacteria in the culture will cause a wheat-based dough, whose gluten has been developed sufficiently to retain gas, to leaven or rise. Obtaining a satisfactory rise from sourdough, however, is more difficult than with packaged yeast, because the lactobacteria almost always outnumber the yeasts by a factor of 100 to 1000, and the acidity of the bacteria inhibit the yeasts' gas production. The acidic conditions, along with the fact that the bacteria also produce enzymes which break down proteins, result in weaker gluten, and a denser finished product.McGee, Harold (2004). On Food and Cooking: The Science and Lore of the Kitchen, 544. New York: Scribner. ISBN 0-684-80001-2

History of sourdough

Sourdough has been used since ancient times with a variety of grains.

Bread made from 100% rye flour, which is very popular in the northern half of Europe, is always leavened with sourdough. Baker's yeast is not useful as a leavening agent for rye bread, as rye does not contain enough gluten; sourdough, however, in lowering the pH level of the dough, causes the starch to partially gelatinize, enabling it to retain gas bubbles. In the southern part of Europe, where baguette and even panettone were originally made with sourdough, it has been replaced by the faster growing yeast.

Sourdough was the main bread made in Northern California during the California Gold Rush, and it remains a major part of the culture of San Francisco. The bread became so common that sourdough became a general nickname for the gold prospecters. The nickname remains in Sourdough Sam, the mascot of the San Francisco 49ers.

See also

  • Amish Friendship Bread, which uses a sourdough starter that includes sugar and milk, and also uses baking powder and baking soda.

External links

References

Breads | Leavening agents

Sauerteig | Surdej | Levain | Zuurdesem | Surdeg | Pasta_madre

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Sourdough".

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