From the bestselling authors of the ground-breaking Artisan Bread in Five Minutes a Day comes a much-anticipated new cookbook featuring their revolutionary approach to yeast dough in over 100 easy pizza and flatbread recipes.
Bread made from 100% rye flour, 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 pentosans; 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 baking. 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.[8] In the southern part of Europe, where panettone is still made with sourdough as leavening,[7] sourdough has become less common in the 20th century; it has been replaced by the faster-growing baker's yeast, sometimes supplemented with longer fermentation rests to allow for some bacterial activity to build flavor.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 fermentation has re-emerged as a major fermentation process in bread production in the past ten years although it is commonly used in conjunction with baker's yeast as leavening agent.[9]
flour water salt yeast the fundamentals of artisan bread and pizza pdf 31
In English-speaking countries, where wheat-based breads predominate, sourdough is no longer the standard method for bread leavening. It was gradually replaced, first by the use of barm from beer making,[14] then, after the confirmation of germ theory by Louis Pasteur, by cultured yeasts.[15] Although sourdough bread was superseded in commercial bakeries in the 20th century, it has undergone a revival among artisan bakers and, more recently, in industrial bakeries.[9][16] In countries where there is no legal definition of sourdough bread, the dough for some products named or marketed as such is leavened using baker's yeast or chemical raising agents as well as, or instead of, a live sourdough starter culture. The Real Bread Campaign calls these products sourfaux.[17][18]
The preparation of sourdough begins with a pre-ferment (the "starter" or "leaven", also known as the "chief", "chef", "head", "mother" or "sponge"), a fermented mixture of flour and water, containing a colony of microorganisms including wild yeast and lactobacilli.[24] The purpose of the starter is to produce a vigorous leaven and to develop the flavour of the bread. In practice there are several kinds of starters, as the ratio of water to flour in the starter (hydration) varies. A starter may be a liquid batter or a stiff dough.[25]
Flour naturally contains a variety of yeasts and bacteria.[26][27] When wheat flour comes into contact with water, the naturally occurring enzyme amylase breaks down the starch into the sugars glucose and maltose, which sourdough's natural yeast can metabolize.[28] With sufficient time, temperature, and refreshments with new or fresh dough, the mixture develops a stable culture.[24][29] This culture will cause a dough to rise.[24] The bacteria ferment starches that the yeast cannot metabolise, and the by-products, chiefly maltose, are metabolised by the yeast, which produces carbon dioxide gas, leavening the dough.[30][31][32][33][34][note 1]
The ratio of fermented starter to fresh flour and water is critical in the development and maintenance of a starter. This ratio is called the refreshment ratio.[44][45] Higher refreshment ratios are associated with greater microbial stability in the sourdough. In San Francisco sourdough, the ratio[46] is 40% of the total weight, which is roughly equivalent to 67% of the new-dough's weight. A high refreshment ratio keeps acidity of the refreshed dough relatively low.[43] Acidity levels of below pH 4.0 inhibit lactobacilli and favour acid-tolerant yeasts.[citation needed]
Bakers have devised several ways of encouraging a stable culture of micro-organisms in the starter. Unbleached, unbromated flour contains more micro-organisms 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 or whole wheat flour or "seed" the culture using unwashed organic grapes (for the wild yeasts on their skins). Grapes and grape must are also sources of lactic acid bacteria,[57][58] as are many other edible plants.[59][60] Basil leaves are soaked in room-temperature water for an hour to seed traditional Greek sourdough.[61] Using water from boiled potatoes is said to increase the activity of the bacteria by providing additional starch.[citation needed]
The starter must be fed 4 to 12 hours prior to being added to dough, by mixing flour and water to the starter. This creates an active leaven, which should grow in size and is ready to use when it is bubbly and floats in water. The leaven is mixed with flour and water to make a final dough of the desired consistency. The starter weight is usually 13% to 25% of the total flour weight, though formulas may vary.[56][67][68] The dough is shaped into loaves, left to rise, and then baked. A number of 'no knead' methods are available for sourdough bread. Due to the length of time sourdough bread takes to proof, many bakers may refrigerate their loaves prior to baking. This process is known as 'retardation' to slow down the proofing process. This process has the added benefit of developing a richer flavoured bread.[citation needed]
Sourdough is a stable culture of lactic acid bacteria and yeast in a mixture of flour and water. Broadly speaking, the yeast produces gas (carbon dioxide) which leavens the dough, and the lactic acid bacteria produce lactic acid, which contributes flavor in the form of sourness. The lactic acid bacteria metabolize sugars that the yeast cannot, while the yeast metabolizes the by-products of lactic acid fermentation.[69][70] During sourdough fermentation, many cereal enzymes, particularly phytases, proteases and pentosanases, are activated through acidification and contribute to biochemical changes during sourdough fermentation.[1]
Most standard bread recipes are made up of only flour, water, salt, and yeast or sourdough starter. The salt percentage tends to stay around the 2% range for most bread recipes. However the amount of yeast/starter and water can vary greatly. 2ff7e9595c
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