Some bakers say it's the taste, others the way it chews that has caused the modern proliferation of sourdough bread, from everyday white sourdoughs sold in supermarkets to voluptuous, earthy whole-grain loaves.
Sourdough starters originally were made from water and flour, and wild yeasts from the air would find their way into the container, causing fermentation after a few days.A portion of the starter is used to make bread, and the rest can be kept going indefinitely by refrigerating it and replenishing it with flour and water. A starter that turns pink or develops an unpleasant odor should be discarded.
It's harder for home bakers to make great sourdough unless they bake often, because long-used starter develops a depth and finesse that new starters don't have, says Marion Cunningham, author of "The Fannie Farmer Baking Book" and other books.
Doughs made in different places have different tastes - possibly because of differences in water, wild yeasts or flours.
In the 1970s, federal food research technologists identified the San Francisco bacteria, which some bakers say is responsible for the distinctive taste there. Bakeries in the city have been producing sourdough bread for nearly 150 years, and the original '49ers - the miners - were nicknamed sourdoughs.
This is an unusual starter in that it includes yogurt. It's from "The Fannie Farmer Baking Book," by Marion Cunningham, from a technique developed by Jerry DiVecchio and Kandace Reeves of Sunset magazine, with the help of George York, food chemist at the University of California, Davis.
Always let the starter come to room temperature before using, which takes several hours. Get it out the night before if you plan to bake in the morning.
To replenish the starter: So you will always have an ample supply, replenish the starter each time you use by adding equal amounts of warm milk and flour. For example, if you used one cup starter, use one cup skim milk and add it to the starter with one cup flour. Stir until smooth. Cover tightly and let stand in a warm place for a few hours or overnight - until bubbly - then cover and store in the refrigerator.
If you bake infrequently, discard about half of the starter every few weeks and replenish it with warm milk and flour. It can also be frozen for a month or two, but this slows down the fermenting process considerably. If the starter was frozen, let stand in a warm place for about 24 hours, or until bubbly, before using.
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RECIPE
SOURDOUGH STARTER
1 cup skim milk
3 tablespoons low-fat yogurt
1 cup all-purpose flour
Heat the milk to 90 degrees to 100 degrees. Remove from heat and stir in the yogurt. Pour into a warmed container and cover tightly. Place in a warm spot (80-100 degrees, but not above 110 degrees). Good spots are on the top of water heaters, in a gas oven with just the pilot light on or in an electric oven with the interior light on - any partially sheltered area where heat collects. After six to eight hours, the mixture will clabber, forming a soft curd that does not flow readily when the container is tilted slightly. Check the mixture periodically, and if a clear liquid rises to the surface, stir it back in. If it has turned light pink in color, it has begun to spoil; discard and begin again.
After the curd has formed, add the flour and stir until smooth. Cover tightly and set in a warm place again. Let stand for two to five days, until the mixture is full of bubbles and has a good sour smell. The starter is ready to use as directed in a recipe.