Ball of dough with flour on wooden surface
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Sourdough breads begin with a starter created by wild yeasts, though some variations use dried yeast or a premade starter base to speed up the fermentation process. It takes several days to develop a starter, but once done, and properly maintained, you can use your sourdough base for several years. Sourdough starters require you to pay scrupulous attention to your equipment. You want yeast to grow in your starter, not bacteria. Should bacteria contaminate the mixture, your sourdough starter will go bad, and you should discard it to avoid illness. Learn the signs of a bad sourdough starter before you prepare your base.

Prepare your sourdough starter using either wild yeasts or dried yeast.

Closely examine your sourdough starter for color. Dark brown or pink starters have been contaminated. Immediately throw out the entire batch as this indicates the starter has gone bad.

Smell your sourdough starter before each use. Expect the smell of fresh unbaked bread dough, or a yeast-like odor. Throw away your sourdough starter if you detect any foul, moldy or decaying odors.

Keep fresh-smelling and pale sourdough starter even if it has not bubbled. Feed it over two days to revive the starter, especially if you store the starter in the freezer or refrigerator.

Feed your starter every day if kept on the counter or once a week if refrigerated. Remove one cup of the starter every day and use this for bread or discard it. Stir in 1 cup of water into the starter and an additional cup of fresh flour. Cover until the next day, when you feed it again.