The Rise of Sourdough
Prefermented breads are becoming increasingly popular over the last few years, and we can expect that trend to continue to rise.
What is a Preferment?
A preferment is a preparation of a portion of bread dough that is made several hours or more before mixing the final dough. City Bakery uses the preferment sourdough (or levain or mother dough) to make many of our breads. In the United States, sourdough and levain are often used interchangeably. However, in Germany, sourdough (or sauerteig) always refers to a culture of rye flour and water; while, in France, the word "levain" refers to a culture that is entirely made out of white flour. What's most important is that they're both a culture of naturally occurring yeasts and bacteria that leaven and flavor bread.
Sourdough and levains are different from other preferments like poolish and pâte fermentée in that they can be perpetuated for months, years, decades and even centuries! For example, Boudin Bakery in San Francisco, who created the "Original San Francisco Sourdough French Bread" in 1849, is said to have used a part of its original mother dough in every single loaf of bread over the last 160 years!
In the Bakery, the baker mixes a small dough of flour and water and freshens it with new food and water in order to develop a colony of microorganisms that ferment and multiply. It's crucial to do this on a consistent schedule. Overtime, these organisms will consume the natural sugars found in the flour, thus, you must periodically feed the levain in order to prevent the organisms from exhausting the sugar supply in it. In order to retain the purity of the culture, a small portion of ripe starter is taken off before mixing the final dough. This uncontaminated portion is then used to make the next batch of bread.
Sometime during the initial stages in the development of a sourdough or levain culture, it is common to see grapes or blueberries, potato water, grated onions, and other items added. However, this is not required for success and is unnecessary. Flour and water are enough to start a levain, as the flour should supply the needed nutrients to grow the colony.
Sourdough's Rise in Popularity
Sourdough breads have made a comeback in recent years due to the rising trend of fermented foods such as sauerkraut, kimchi, and kobmucha, and as U.S. consumers seek out authentic, rustic foods and ingredients - such as breads with more savory, complex flavors than commercialized breads that use chemical leaveners, which are used to speed up the leavening process.
In addition to the flavor, sourdough may also have some health benefits. In the long slow fermentation that produces sourdough bread, important nutrients such as iron, zinc and magnesium, antioxidants, folic acid and other B vitamins become easier for our bodies to absorb. Therefore, examples have shown that sourdough breads may be easier to digest and for micro-nutrient absorption.