Sourdough 189345 225140387 2008-07-12T02:32:48Z Xnatedawgx 4789380 category update [[Image:Masa madre.jpg|thumb|right|300px|Sourdough starter made with flour and water refreshed for 3 or more days]] '''Sourdough''' (or, more formally, ''natural leaven'' or ''[[levain]]'') refers to the process of [[leavening agent|leavening]] [[bread]] by capturing wild [[yeast]]s in a dough or batter, as opposed to using a domestic, purpose-cultured yeast such as [[Saccharomyces cerevisiae]]. '''Sourdough''' more specifically refers to a [[symbiosis|symbiotic]] culture of [[lactobacillus|lactobacilli]] and [[yeast]]s, giving a distinctively tangy or sour taste (hence its name), due mainly to the [[lactic acid]] and [[acetic acid]] produced by the lactobacilli. Though no longer the standard method for bread leavening in most developed countries (it was gradually replaced first by the use of [[barm]] from [[beer]]making, then after the confirmation of [[germ theory]] by [[Louis Pasteur]] by cultured yeasts), some form of natural leaven is used in many specialty bakeries. Sourdough bread is made by using a small amount (20-25%) of "[[Bread starter|starter]]" dough (sometimes known as "the mother sponge"), which contains the yeast culture, and mixing it with new [[flour]] and water. Part of this resulting dough is then saved to use as the starter for the next batch. As long as the starter [[dough]] is fed flour and water daily, the sourdough mixture can stay in room temperature indefinitely and remain healthy and usable. It is not uncommon for a baker's starter dough to have years of history, from many hundreds of previous batches. As a result each bakery's sourdough has a distinct taste. The combination of starter, yeast culture and air temperature, humidity, and elevation also makes each batch of sourdough different. == Biology and chemistry of sourdough == [[Image:Sourdough miche & boule.jpg|thumb|right|250px|Two loaves of naturally-leavened (sourdough) bread.]] A sourdough [[Bread starter|starter]] is a stable symbiotic culture of [[bacteria]] and yeast present in a mixture of [[flour]] and [[water]]. The yeasts ''Candida milleri or Saccharomyces exiguus'' usually populate sourdough cultures symbiotically with ''Lactobacillus sanfranciscensis.''<sup>[http://aem.asm.org/cgi/content/full/64/7/2616]</sup>. ''[[Lactobacillus sanfranciscensis]]'' (bacteria) was named for its discovery in San Francisco sourdough starters. Often a starter will consist of basic items such as: water, bread flour, [[rye]] flour and a sourdough starter which can be purchased at certain grocery stores. Once the starter is made water and flour must be added in time increments over a period of days. Depending on the locale of the bakery and the type of bread being made, the starter can be either a relatively fluid batter or a stiffer dough; as a general rule, the more sour breads are made with a liquid starter. Firm starters (such as the Flemish [[Desem]] starter) are often more resource-intensive, traditionally being buried in a large container of flour to prevent drying out. 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 ([[sucrose]] and [[maltose]]); [[maltase]] converts the sugars into [[glucose]] and [[fructose]] that yeast can metabolize. The lactobacteria feed mostly on the metabolism products from the yeast. <ref name="rosada">Rosada, Didier (1997) ''Advanced Sourdough''. Minneapolis: National Baking Center.</ref> The mixture develops a balanced, symbiotic culture after repeated feedings. There are several ways to increase the chances of creating a stable culture. [[Flour_bleaching_agents|Unbleached]], [[Potassium_bromate|unbromated flour]] contains more microorganisms than more processed flours. [[Bran]]-containing (wholemeal) flour provides the greatest variety of organisms and additional minerals, though some cultures use an initial mixture of white flour and rye flour or "seed" the culture using unwashed organic [[grapes]] (for the wild yeasts on their skins). Using water from boiled [[potato|potatoes]] also increases the leavening power of the bacteria, by providing additional starch. Bakers recommend un-chlorinated water for feeding cultures. Adding a small quantity of diastatic malt provides maltase and simple sugars to support the yeasts initially.<ref name="reinhart">Reinhart, Peter (1998) ''Crust & Crumb: Master formulas for serious bread bakers''. Berkeley: Ten Speed Press. ISBN 1-58008-003-0</ref> 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 [[bacterium|bacteria]] as a result of its [[acid]]ity 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 between 100 and 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.<ref>McGee, Harold (2004). ''On Food and Cooking: The Science and Lore of the Kitchen'', 544. New York: Scribner. ISBN 0-684-80001-2</ref> ==Preparing sourdough products== Sourdough starter can be used in two different manners. Traditionally, a certain amount of sourdough starter (somewhere around 20-25% on average, depending on the water content of the starter) is mixed into the bread dough, and the bread is kneaded and allowed to rise as normal. The process is largely similar to using a pure strain of baker's yeast, although some care must be taken since the rise time of most sourdough starters is usually somewhat longer than the average for typical baker's yeasts. (As a result, many sourdough starters are unsuitable for use in a [[bread machine]].) When using a particularly liquid starter with a high concentration of lactobacillus or acetobacter organisms, the large amount of lactic and acetic acids produced needs to be managed carefully, since the acid can break down the gluten in the bread dough; this becomes less of a concern in a stiffer starter, where the yeast usually predominates. The other manner of using sourdough starter is common for making [[quick bread]]s or foods like [[pancake]]s. It involves using [[baking soda]] (and sometimes [[baking powder]]) to neutralize some or all of the acid in the starter, with the acid-base reaction generating [[carbon dioxide]] to provide lift to the dough or batter in a manner very similar to [[Irish soda bread]]. This technique is particularly common in kitchens where the starter is intentionally kept off-balance, with a substantially high acid level, and is particularly associated with areas such as Alaska. == History of sourdough == [[image:sourdoughbread.jpg|right|130px|thumb|Sourdough bread]] Sourdough likely originated in [[Ancient Egyptian cuisine|Ancient Egyptian]] times around 1500 BC, and was likely the first form of leavening available to bakers. Sourdough remained the usual form of leavening down into the European [[Middle Ages]]<ref>Hieatt, Constance et al., ''Pleyn Delit'', 2ed, Toronto: University of Toronto Press, 1996, ISBN 0802076327.</ref> until being replaced by [[barm]] from the beer brewing process, and then later purpose-cultured yeast. Bread made from 100% [[rye]] flour, which is very popular in the northern half of [[Europe]], is usually leavened with sourdough. Baker's yeast is not useful as a [[leavening agent]] for rye bread, as rye does not contain enough [[gluten]]. The structure of rye bread is based primarily on the [[starch]] in the flour, as well as other carbohydrates known as [[pentosan]]s; however, rye [[amylase]] is active at substantially higher temperatures than wheat amylase, causing the structure of the bread to disintegrate as the starches are broken down during cooking. The lowered [[pH]] of a sourdough starter therefore inactivates the amylases when heat cannot, allowing the carbohydrates in the bread to gel and set properly.<ref>Wing, Daniel, and Alan Scott. ''The Bread Builders'', White River Junction (VT), Chelsea Green Publishing, 1999.</ref> In the southern part of Europe, where [[baguette]] and even [[panettone]] were originally made with wheat flour and rye flour has become less common as the standard of living has risen, it has been replaced by the faster growing baker's yeast, sometimes supplemented with longer fermentation rests to allow for some bacterial activity to build flavor. Sourdough was the main bread made in [[Northern California]] during the [[California Gold Rush]], and it remains a part of the culture of [[San Francisco, California|San Francisco]] today. The bread became so common that "sourdough" became a general nickname for the gold prospectors. The nickname remains in "[[Sourdough Sam]]", the [[mascot]] of the [[San Francisco 49ers]]. The sourdough tradition was carried into Alaska and the western Canadian territories during the [[Klondike Gold Rush]]. Conventional leavenings such as yeast and baking soda were much less reliable in the conditions faced by the prospectors. The sourdough starter, however, had to be kept warm to survive. Experienced miners and other settlers frequently carried a pouch of starter either around their neck or on a belt and were often fiercely guarded. Old hands came to be called "sourdoughs", a term that is still applied to any Alaskan old-timer. [http://editore.slowfood.com/editore/riviste/slow/EN/34/sourdoughs.html] San Francisco sourdough is the most famous sourdough bread made in the US. In contrast to the majority of the country, it has remained in continuous production for nearly 150 years, with some bakeries able to trace their starters back to California's territorial period. It is a white bread, characterized by a pronounced sourness (not all varieties are as sour as the San Francisco sourdough), so much so that the dominant strain of lactobacillus in sourdough starters was named ''Lactobacillus sanfranciscensis''. Sourdough also became popular because of its ability to combine well with seafoods and soups such as [[cioppino]], clam chowder and chili. Sourdough has not enjoyed the popularity it once had since bread became mass-produced. Manufacturers make up for the lack of yeast and bacteria culture by introducing an artificially-made mix known as [[bread improver]] into their dough. == Sourdough breads == Aside from what might be called plain sourdough bread, there are a number of other breads that use similar starters and techniques. [[Amish Friendship Bread]] uses a sourdough starter that includes [[sugar]] and [[milk]]. However, it is further leavened with [[baking powder]] and [[baking soda]], making it more of a [[quick bread]]. The German [[Pumpernickel]], is traditionally made from a sourdough starter, although modern pumpernickel loaves often use commercial yeasts, sometimes spiked with [[citric acid]] or [[lactic acid]] to inactivate the [[amylase]]s in the rye flour. Also, the Flemish [[Desem]] bread is a popular form of whole-wheat sourdough, though cultured in a much less liquid medium. Other recipes use starters that aren't actually truly natural leavens. The Italian [[Biga (bread baking)|Biga]] and French [[Poolish]] add sourdough-like flavors to breads by allowing the yeast a lengthy half-day or longer fermentation. Unlike a true sourdough, these recipes usually start with commercial yeast, and cultivation of lactobacillus bacteria is generally an incidental effect. ==See also== *[[Salt rising bread]] *[[Klondike Gold Rush]] where ''sourdough'' was a word for an experinced miner<ref>[http://www.merriam-webster.com/dictionary/sourdough Merriam-Webster online - Sourdough]</ref> ==External links== {{Cookbook|Sourdough Starter}} *[http://www.nyx.net/~dgreenw/sourdoughfaqs.html Usenet rec.food.sourdough FAQ], including further HOWTOs and links to suppliers and recipes *[http://sourdough.com/ Sourdough Companion] - A Sourdough Bread Community, videos and tutorials *[http://aem.asm.org/cgi/content/full/64/7/2616 Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri...] from Applied and Environmental Microbiology, July 1998, by Gänzle et al., Universität Hohenheim *[http://www.artisanbreadbaking.com/breads/sourdough_12_20/sourdough_12_20.htm] Recipe, discussion and pictures of making sourdough bread. *[http://sourdough.com.au/blog/sourdom SourDom's Beginners' Blog] - A series of 5 basic tutorials on sourdough baking *[http://students.washington.edu/neihart/yeast_page01.html The Yeast Beacon] - A tutorial on growing your own sourdough *[http://home.att.net/~carlsfriends/ 1847 Oregon Trail Sourdough Starter] - A source for free sourdough starter. ==References== <references/> [[Category:Sourdough breads| ]] [[Category:Leavening agents]] [[Category:Alaskan cuisine]] [[Category:Culture of San Francisco, California]] [[da:Surdej]] [[de:Sauerteig]] [[es:Masa madre]] [[fi:Taikinajuuri]] [[fr:Levain]] [[he:מחמצת שאור]] [[it:Pasta madre]] [[ja:サワードウ]] [[ko:사워도]] [[nl:Zuurdesem]] [[no:Surdeig]] [[pl:Zakwas chlebowy]] [[sv:Surdeg]]