How to Revive Sourdough Starter

A sourdough starter is an acidic community of natural yeasts and bacteria used to leaven bread and add flavor. Sourdough starter has a lot of nicknames: pre-ferment, levain, leaven, la mère, but it all starts with a bit of flour and water left out to allow the growth of yeast. Most starters also contain lactic acid bacteria—the same bacteria that give yogurt and fermented pickles their tangy flavor.

Making a sourdough starter means that you’re nurturing wild yeast in a small amount of dough. This combination kick-starts fermentation—hence the name “starter”—in sourdough baking. Water activates the wild yeasts in the starter, then the yeasts digest sugars in the flour, which releases carbon dioxide gas. The resulting gas bubbles allow sourdough bread to rise by expanding within the elastic gluten network of bread dough.

These are some of the telltale signs that it’s time to revive your sourdough starter.

1. 1. Discolored alcohol formation: If left alone too long, the yeasts in your starter will start to convert sugar into alcohol, leaving a harsh-smelling syrup on top of a previously healthy sourdough starter. This alcohol isn’t necessarily bad, but if you check the back of the fridge and a purple or black layer of hooch has formed on top, or if your starter smells like nail polish remover, pour off the liquid and feed your starter.
2. 2. Unpleasant smell: Your sourdough starter should have a smell to it, but the smell should be pleasantly yeasty and slightly sour. If it smells acrid or just plain bad (use your judgment), it may be time to refresh your starter.
3. 3. Unresponsive behavior: An active starter should be bubbly and rise and fall after each feeding. If it looks particularly dry or solid—or if it stays at the same level—it’s probably not healthy.
4. 4. Failing the float test: If it’s been a while since you checked in and you want to test the readiness of your starter, fill a small bowl with warm water and drop in a spoonful of starter. If the starter floats, it’s mature enough to help your bread rise. If it sinks, you’ll need to continue the feeding process until the yeast grows strong enough.

Troubleshooting your neglected starter begins with evaluating your materials and starter feeding schedule.

1. 1. Use filtered water. Make sure only to feed your sourdough starter with filtered water, since unfiltered water can contain chlorine that will adversely affect your yeast.
2. 2. Change locations. If your starter is sluggish, consider moving it to a warmer place in your home. If your starter is very active and quickly forms alcohol, consider moving it somewhere a little cooler. If you’re going on vacation, store your sourdough starter in the refrigerator until you get back.
3. 3. Try a more nutritious diet. If your starter has been subsisting on white flour or bread flour alone, adding a little rye flour or whole wheat flour to your starter’s diet can increase activity.
4. 4. Stick to a regular feeding schedule. Part of the beauty of caring for a sourdough starter is learning the rhythms of your particular strain of wild yeast and how it responds to its environment. Pay close attention to when your starter rises and falls: You may need to feed it more or less often than you think.
5. 5. Know when to give up. If, when trying to revive your starter, you find that it remains inactive after a few days of regular feedings, your old starter may just be too old, and you should start from scratch. Luckily, a new sourdough starter can be ready in a matter of days, and will contain the same wild yeasts that your old starter picked up from your environment.
6. 6. Stop if your starter gets moldy. Sourdough starters can largely be rescued, even if they smell bad or are covered with a thick layer of hooch. But if you see fuzzy black or green mold on your starter, you should discard the entire batch. The spores may have already penetrated the entire starter, and it’s no longer safe to use.

Follow this step-by-step tutorial to revive your sourdough starter.

1. 1. Remove the hooch. If your sourdough starter has developed an unhealthy-looking layer of alcohol, pour it off. Likewise, if your starter has formed a crust, remove it.
2. 2. Discard. Discard most of your existing starter (including any discolored portions) until you’re left with two ounces of starter (about a quarter cup).
3. 3. Feed your remaining starter. Transfer the starter to a glass jar or other clean vessel. Every twelve hours, feed it with equal parts flour and water—for example, two and a half ounces of unbleached all-purpose flour (just over a quarter of a cup of flour) and a quarter of a cup of water (two ounces). Between feedings, cover it with plastic wrap, a lid, or a clean kitchen towel secured with a rubber band and store it at room temperature.
4. 4. Check for signs of life. Once your starter smells yeasty and sweet (rather than offensive) and doubles in size every eight to twelve hours, it’s ready to use again. Transfer it to a clean jar.

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