Care and feeding of your starter
To keep bacteria and yeasts healthy, the yogurt starter must be nourished occasionally with flour and milk.
Environment. When creating the starter, incubate it between 80° and 90°. Any hotter and the bacteria may die; any cooler and the starter could develop mold. Set it on top of your water heater, on a counter with a lamp warming it, or in an oven warmed with pans of boiling water. An established starter is stronger; after feeding, it can stand at room temperature.
To feed the starter and keep it going. For best results, try to feed the starter at least once a month, even if you’re not baking. To feed, add warm (90° to 100°) nonfat or low-fat milk and all-purpose flour to the starter, each in quantities equal to what you’ll be using in the recipe. For example, if the recipe calls for 1 cup starter, add 1 cup milk and 1 cup flour. (This is also the right amount for a monthly feeding even if you’re not baking.) Cover tightly and let stand in a warm (80° to 90°) place until bubbly and sour-smelling and a clear liquid has formed on top, 12 to 24 hours. The clear liquid shows that the acid level has risen and is starting to break down milk protein, and high acid means sour flavor. Use at this point (just give it a stir first) or cover and chill.
To increase the starter supply (for gift-giving or quantity baking), you can add up to 10 cups each of milk and flour to 1 cup of starter (use a large container). The mixture may need to stand up to 2 days before the clear liquid forms on top.
Sourdough starter FAQs
What if I neglect my starter?
Even with the best intentions, it’s easy to forget to feed a starter, but they can be surprisingly resilient. If you rediscover yours in the back of the fridge, take its “pulse.” An “old” smell, no bubbles at room temperature, a top layer of dark brown liquid, or slight mold growth indicate your starter isn’t feeling its best. First spoon off and discard any mold, then stir the starter. Feed it 1 cup each of flour and milk and let stand as directed in To Feed the Starter and Keep It Going, left. After 24 hours, discard half the starter and repeat feeding and standing. Repeat a third time, if needed, until the starter bubbles and has a “fresh” sour smell. If, after repeated feedings, your starter still smells “off” and won’t bubble, throw it away. Also begin a new starter if mold growth is heavy.
Can you use a starter too often?
Overuse isn’t a problem per se; if you bake several times a week or feed your starter a lot all at once (to increase quantity), it may take longer than usual to regain normal sourness. After feeding, let it stand as directed in To Feed the Starter and Keep It Going, left.
Why do starters “die”?
The longer a starter stands without new food, the higher the acidity gets; too much acid, and beneficial bacteria can’t survive. Mold infestations may also kill off good bacteria.
Can I freeze it when I’m not going to use it for a while?
Starters generally freeze successfully for up to a few months, but freezing does change the bacteria’s cell structure. Longer freezing brings more changes and decreases the chance of success with the thawed starter.