The characteristic flavor of sourdough is not due to yeast, but to the presence of a harmless bacteria naturally present in raw milk, aged Cheddar cheese, cultured buttermilk, and yogurt. We tried making starters with all of these products and decided yogurt was the easiest to work with. But within the first 6 months, you will have more success with your new sourdough starter if you use it in recipes that also include yeast.

Start with 1 1/2-quart container - glass, pottery, rigid plastic, or stainless steel. Warm the container by letting hot water stand in it for several minutes; then wipe dry.

Heat 1 cup skim or low-fat milk to 90 to 100 degrees. Remove from heat; stir in 3 tablespoons unflavored, low-fat yogurt. Pour milk mixture into warm container, cover tightly; let stand in a warm (80 to 100 degrees) place - on top of a water heater, near the burner of a gas range (not on it), or atop a built- in refrigerator (if there's room).

Within 18 to 24 hours, starter should be about the consistency of yogurt (a curd forms and mixture does not flow readily when container is slightly tilted). If a clear liquid rises to top of milk, stir it back in; but if liquid has turned light pink, it indicates that milk is beginning to break down, so discard and start over.

After a curd has formed, gradually stir in 1 cup all-purpose flour into starter until smoothly blended. Cover tightly and let stand in a warm place (80 to 100 degrees) until mixture is full of bubbles and has a sour smell; this takes 2 to 5 days. If clear liquid forms during this time, stir it back into starter. But if liquid turns pink, discard all but 1/4 cup of starter. Blend in a mixture of 1 cup each warm milk (90 to 100 degrees) and all-purpose flour. Cover tightly and let stand again in warm place until bubbly then it's ready to use. Or cover and store in refrigerator. This makes 1 1/2 cups starter.

Always let your starter warm to room temperature before using (this takes about 4 to 6 hours). You can leave it out overnight to use first thing in the morning.

To maintain an ample supply, each time you use part of your starter, replenish it with equal amounts of warm milk (90 to 100 degrees) and all-purpose flour. (If you use 1/2 cup starter, blend in a mixture of 1/2 cup each warm milk and all-purpose flour.) Cover and let stand in a warm place for several hours or overnight, until it is again full of bubbles; then store in the refrigerator.