HOME COOK : Lactobacillus: The San Francisco Treat

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.

After curd has formed, add flour and stir until smooth. Cover tightly and set in warm place again. Let stand 2 to 5 days, until mixture is full of bubbles and has good sour smell. At this point, starter is ready to use as directed in recipes.

Always let starter come to room temperature before using, which takes several hours. Take out night before if you plan to bake in morning. Makes 1 1/2 cups starter.


To Replenish Starter

For an ample supply, replenish the starter each time you use it by adding equal amounts of warm milk and flour. For example, if you used 1 cup starter, warm 1 cup skim milk and add it to the starter with 1 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 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 action considerably. If the starter was frozen, let it stand in a warm place for about 24 hours, or until bubbly, before using.



1 loaf Sourdough White Bread, cut into 12 slices

4 large cloves garlic, peeled

6 tomatoes, finely chopped

1 cup fresh basil leaves, finely chopped



1/2 cup olive oil

Spread Sourdough White Bread slices on baking sheet and place under broiler to toast on both sides. Remove and rub each slice with garlic clove. Combine tomatoes and basil. Mash mixture with fork.

Season to taste with salt. Place tomato mixture in sieve and press out excess tomato juice. Brush olive oil generously over garlic-rubbed toast and spread tomato mixture on top. Serve at room temperature. Makes 6 servings.


Each serving contains about:

408 calories; 499 mg sodium; 2 mg cholesterol; 21 grams fat; 49 grams carbohydrates; 8 grams protein; 0.99 gram fiber.


4 cups spinach leaves, washed, dried, trimmed of stems


4 tomatoes, trimmed and sliced 1/4-inch thick

2 red onions, sliced thin in rings


1/4 cup olive oil


1 1/2 tablespoons vinegar

1/2 teaspoon freshly ground black pepper

1 tablespoon prepared horseradish

Arrange bed of spinach leaves on serving platter. Top with tomato slices and then onion rings. Sprinkle salt to taste evenly over all.


Combine oil, vinegar, pepper and horseradish in small bowl and beat until blended. Pour dressing over salad. Makes 4 servings.

Each serving contains about:

175 calories; 134 mg sodium; 0 cholesterol; 14 grams fat; 12 grams carbohydrates; 3 grams protein; 1.57 grams fiber.



3 eggs

1/2 cup milk

1/2 teaspoon nutmeg

1/4 teaspoon salt


2 cups cornflakes, slightly crumbled

6 slices Sourdough White Bread

4 tablespoons butter

6 tablespoons sugar


Stir eggs, milk, nutmeg and salt together in bowl until well blended. Strain mixture through sieve into bowl shallow enough to dip bread easily. Spread cornflakes on piece of wax paper. Dip (don’t soak) both sides of each bread slice into milk batter. Then press both sides of each bread slice into cornflakes to coat bread well.

Melt 2 tablespoons butter in 12-inch skillet over medium heat and fry 3 coated bread slices until golden on each side. When done, sprinkle about 1 tablespoon sugar on top of each slice. Keep warm in 225-degree oven while other slices fry in remaining butter. Serve hot. Makes 4 servings.

Each serving contains about:

440 calories; 741 mg sodium; 194 mg cholesterol; 17 grams fat; 59 grams carbohydrates; 11 grams protein; 0.15 gram fiber.