Items you will need
Having a live sourdough starter in your refrigerator is a commitment. A sourdough starter needs to be fed regularly, and if you don't use it in your baking you need to take out its waste. Sourdough starter contains organisms like bacteria and yeast. If the bacteria grow too numerous, they can cause overly acidic flavors, a foul smell or separation of liquids. You don't ever need to throw out your sourdough starter. Replenish your starter culture by regrowing it until the organisms are back in balance.
Mix the sourdough bread starter well. Mixing oxygenates your sourdough starter and helps it to remain healthy. If you see a gray or brown liquid on top of the starter, pour it off before mixing.
Discard all but 1 cup of the starter.
Add 1 cup of room temperature water to the remaining starter. Stir well. Watering down the sourdough starter dilutes the lactic acid and bacterial byproducts that inhibit yeast growth. Once your yeast is healthy again, it will keep the bacteria levels in check.
Pour out all but 1 cup of the mixture.
Add 1 cup of flour and 3/4 cup of water to the liquid starter and mix thoroughly. Cover the mixture loosely and let it proof on the counter overnight. Flour provides food for your yeast to thrive on.
Check for bubbles in the starter in the morning. They indicate that fermentation has restarted. When your starter’s good sour smell returns, healthy yeast growth is in progress.
Perform the steps again if you do not see bubbles in the starter.
Once it becomes healthy again, feed your sourdough starter at least once a week, or whenever you use it, whichever comes first.
If your starter smells bad, it probably is. Start the entire replenishment process over from the beginning.