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HOME COOK : Lactobacillus: The San Francisco Treat

September 24, 1992|MARION CUNNINGHAM

The mystery of what makes San Francisco sourdough bread was not solved by a Sherlock Holmes or an Agatha Christie, but rather by a remarkable sleuth, Leo Kline, and his assistant, T. Frank Sugihara. This detective story began in 1969 at the Western Regional Research Center of the U. S. Department of Agriculture in Albany, Calif.

The microbiologist detective decided it was time to solve the puzzle of what specific microorganisms create San Francisco sourdough bread. Most believed that the miracle of San Francisco sourdough was achieved by yeast that wafted into the Italian brick bakeries on gentle Bay breezes and lived in the bricks and in the sourdough starters. After months of investigation, the story that Kline unveiled was much more incredible than breezes and bricks.

Sourdough contains bacteria and yeast. Normally there are about a dozen identifiable bacteria in every sourdough culture, but Kline found a totally unknown one, which he named Lactobacillus sanfrancisco, in five San Francisco sourdough breads: Parisian, Toscana, Colombo, Baroni and Larraburu.

He also discovered that San Francisco sourdough is the only bread with just one bacteria, which works symbiotically with the yeast. This yeast/bacteria relationship is like the old Mother Goose rhyme, "Jack Sprat could eat no fat, his wife could eat no lean. And so betwixt them both, they licked the platter clean."

The San Francisco sourdough yeast, Saccharomyces exiguus , tolerates the acetic acid and won't touch the sugar (maltose) that Lactobacillus sanfrancisco eats. This is a reversal of the usual situation, where the yeast that makes a bread rise cannot tolerate a high level of acetic acid and exists on sugar.

Kline also discovered why those before him had had such difficulties isolating the San Francisco bug: It took him several months and 30 different substances before he could find a medium that the bacteria would grow out on.

When I recently spoke to Kline, I mentioned how wonderful it would be if we home cooks could buy the San Francisco dried sourdough starter and make this bread at home. He said this might well be a possibility, since the full application of his discovery is yet to be made. Meanwhile, we at home do have an unusually good sourdough starter or sponge (the terms are interchangeable) that was created by Dr. George York, food chemist at the University of California at Davis, with the help of Kandace Reeves and Jerry Anne Di Vecchio from Sunset Magazine.


1 1/4 cups warm water

1 cup Sourdough Starter, at room temperature

About 5 cups flour

1 tablespoon salt

2 tablespoons cornmeal

Combine warm water, Sourdough Starter and 2 1/2 cups flour in large mixing bowl. Beat until smooth, cover with plastic wrap and let stand in warm place, at about 85 degrees (in gas oven with pilot light on, or electric oven with interior light on, or on top of water heater) 8 hours or overnight, until thick, full of bubbles and spongy looking.

Add salt and enough remaining flour to make fairly stiff, manageable dough. Turn out onto lightly floured surface and knead 1 to 2 minutes. Let stand 10 minutes.

Resume kneading about 10 minutes, until smooth and elastic, adding just enough flour to keep dough from being too sticky. Place in greased bowl, cover and let rise in warm place until doubled in bulk.

Punch dough down and divide in halves. Plump each piece into round, then draw hands down sides, stretching dough toward bottom and turning as you work. Continue stretching and turning until round is perfectly smooth. Pinch bottom of loaves firm where seams come together. Sprinkle large baking sheet with cornmeal and top with formed loaves, pinched-side down. Cover loosely and let rise until double in bulk.

With razor blade or sharp knife, slash 1/2-inch-deep X across top of each risen loaf, then spray or brush with cold water. Place in 375-degree oven and bake 10 minutes, then brush or spray with cold water again. Bake 10 minutes more and brush or spray again. Bake 40 minutes more (total baking time is 1 hour), then transfer to racks to cool. Makes 2 medium-size round loaves, about 8 servings per loaf.

Each serving contains about:

170 calories; 454 mg sodium; 0 cholesterol; 1 gram fat; 35 grams carbohydrates; 5 grams protein; 0.14 gram fiber.

Sourdough Starter

1 cup skim milk

3 tablespoons plain low-fat yogurt

1 cup flour

Heat milk to 90 to 100 degrees. Remove from heat and stir in yogurt. Pour into warmed container and cover tightly. Place in warm spot, 80 to 100 degrees, but not above 110 degrees. (Good spots are on top of water heaters, in gas oven with pilot light on, or in electric oven with interior light on.)

After 6 to 8 hours, mixture will clabber, forming soft curd that does not flow readily when container is tilted slightly. Check mixture periodically, and if clear liquid rises to surface, stir back in. If mixture turns light pink in color, it has begun to spoil; discard and begin again.

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