Sourdough Starter

In a large bowl, combine flour, sugar and yeast. Gradually add water to flour mixture. Stir until smooth. Cover loosely and let stand in a warm place until bubbly and sour-smelling, about 2 days. Starter may darken, but if it changes to another color, discard and start over. To store, cover and refrigerate, which slows down the fermentation of a starter. To replenish and keep starter alive: Once a week, stir in equal amounts of all-purpose flour and warm water (100 to 110 degrees). Beat until smooth. Cover and let stand in a warm place until mixture is bubbly and sour-smelling and a clear liquid has formed on top, about 12 to 24 hours. Use or cover and refrigerate until ready to use.