I avoid referring to my naturally leavened breads as sourdough because too many people associate sourdough with breads that are indeed sour in flavor and sometimes leave a sharp, vinegary aftertaste. In France, sour bread is probably considered a fermentation mistake, while in San Francisco, it’s a well-appreciated taste—although that may be changing. My preference is for complex flavors from the grain and fermentation that are subtle, in balance, and not sour.
A levain can support multiple strains of wild yeast, giving the baker an opportunity to create bread and other leavened baked goods with complex aromas and flavors. Such breads also have a more extended shelf life than breads made from commercial baker’s yeast. The yeast community in a levain culture consists of billions of rapidly reproducing, gas-belching, single-celled organisms. I like knowing that I can make them do what I want them to do.
Bakers feed their levain cultures anywhere from once a day to every few hours. In the following pages, I’ll show you how easy it is to start a new levain culture from scratch using just flour and water and following a once-a-day feeding schedule. Then I’ll explain how to feed an established levain, how to store it in the refrigerator if you won’t be baking with it every day, and how to restore it for its next use.
MANIPULATING FLAVOR
Baking with a levain culture is a fermentation craft similar in some ways to making wine from grapes and their naturally occurring yeasts: each manipulates fermentation to create an end product that meets a desired flavor profile and degree of complexity.
The character of a naturally leavened bread depends on a number of variables: how much water is in the culture, the temperature of the water used each time the culture is fed, the type of flour, the ratio of levain to new flour each time the culture is fed or refreshed, the feeding schedule, the temperature at which the levain is kept, how ripe the levain is, and how much of the levain is used in the final dough. The aroma, flavor, and appearance of levain breads and the consistency of the product from one day to the next are all expressions of the baker’s craft—his or her signature, in a sense. A true artisan baker is someone who understands how to manipulate the relatively small number of variables (which can yield an infinite number of possible results) to produce exactly the bread desired. In this book, I’ll give you specific instructions for making and using a natural levain culture my way, and then I’ll explain how to adjust the variables to suit your own tastes. Levain breads have the potential to be the most personal breads a baker makes.
The complexity of tastes in a levain bread arise from the community of wild yeasts and bacteria in the culture, fermentation gases, lactic and acetic acids, and, of course, time for these things to accumulate. My revelation “less yeast and more time” definitely applies here. Lengthening the fermentation time of levain doughs by retarding them at cooler temperatures greatly improves flavor. So does using smaller amounts of levain and allowing doughs to ferment for a very long time at room temperature. Bacterial fermentation and acidity add desirable tastes and aromas, but only if enough time is allowed for these very complex biochemical reactions to take place.
Acids are responsible for the sourness in sourdough. The vinegary taste comes largely from acetic acid. Lactic acids are common in milk, and indeed contribute a milky or buttery taste to breads. Both acids are often more evident as an aftertaste, unless the sour character is strong and pronounced. Many naturally leavened breads have a flavor profile that leans more toward one end of the acetic-lactic spectrum than the other. San Francisco sourdough is an excellent example of bread with strong acetic character—think “vinegary.” Levain cultures kept in cooler temperatures also lean toward the acetic end of the taste spectrum, as do stiffer levains. Bread made from a liquid levain, with equal parts flour and water (it has a soupy texture), has a distinctive flavor profile that leans toward the lactic acid end of the taste spectrum. Warmer levain cultures encourage lactic acid production, and just like the top-fermented ales that brewers ferment at warmer temperatures, these can produce fermented fruit flavors, especially when they get particularly ripe.
Want a little more detail? Here goes, with a shout-out to Teri Wadsworth and John Paul of Cameron Winery in Dundee, Oregon. The levain is a symbiotic culture of lactic acid bacteria and yeast. Lactic acid bacteria are a diverse group of bacteria that produce lactic acid, carbon dioxide, a small amount of ethanol, and other volatile flavor components as the end product of carbohydrate fermentation. Under the right conditions, lactic acid bacteria can also produce acetic acid. In a levain, the lactic acid bacteria feed mostly on the yeast’s metabolic by-products. As with natural yeast fermentation, time is required for the bacteria to grow and produce acids and other flavor components. Lactic acid bacteria are important in a plethora of fermented foods, including yogurt, beer, pickles, sauerkraut, and cheese, and the acidity they produce inhibits the growth of organisms that can cause spoilage.
I could go on about how alcohol can convert to acetic acid when there is an excess of fermentation, but I don’t want to distract from the main goal, which is to know how to manipulate the variables at play in the kitchen to make good levain bread. At the end of this chapter is a table, Variations in Levain Cultures, summarizing the variables and their impact on taste.

VARIABLES INFLUENCING LEVAIN CULTURES
Hydration
More liquid in the culture leads to greater production of lactic acid. Stiffer cultures have a flavor profile more dominated by acetic acid.
Temperature
Warmer temperatures, meaning 78ºF to 90ºF (26ºC to 32ºC), favor lactic acid production. Cooler temperatures, meaning 55ºF to 65ºF (13ºC to 18ºC), favor acetic acid production. Warmer cultures develop faster.
Flour
High-extraction flours (milled from a larger portion of the wheat berry than pure white flour), whole grain wheat or rye flours, and high-ash flours (which have a high mineral content) all contribute to more vigorous fermentation. They can also create a volatile culture that requires more frequent feedings to prevent problems. Every type of flour—white, whole wheat, rye, and so on—has its own personality, as will different blends of flours.
Salt
Salt delays the fermentation process, and while some good bakers use salt in their levain culture, I prefer not to, as I’m looking for active development. (Still, certain environments or schedules necessitate the use of small amounts of salt.)
Yeast
Commercial yeast is more vigorous than wild yeasts, so adding even a small amount of packaged yeast to start or boost a levain culture will ultimately result in the commercial yeast dominating and eventually starving out the wild yeasts. Bottom line: Don’t use packaged or commercial yeast in a levain culture, either to start it or to maintain it. However, it is okay to use a small amount of baker’s yeast in the final bread dough to supplement the fermentation from the levain culture—so long as the unadulterated levain culture remains separate from the bread dough.