Can You Use Sourdough Starter Discard?

When feeding sourdough starter, take some of the existing starter and mix it with fresh flour and water; set the rest aside. This is necessary because acid builds up in unfed starter, slowing its activity, and the container grows with each feeding. The discarded portion is starter from before feeding: it is hungry, more acidic, and has less leavening power. It cannot make dough rise, but it adds flavor; its uses follow from these two qualities, and much of what gets discarded can actually go into a dough.

Starter discard is easiest to use in doughs that do not need to rise. Replace some of the milk and flour in crepe batter with discard for a slightly tangy flavor. Adding it to flatbread dough makes the dough softer to roll out and gives it a deeper flavor after cooking. For crackers, knead the discard with flour, olive oil, and salt, roll it thin, cut it on the baking sheet, and bake until crisp; sprinkle sesame or nigella seeds on top. The thinner the crackers are rolled, the crispier they will be.

Discard does not work on its own in doughs that need to rise, but it can be used with another leavener. The acid in discard added to pancake or fried-dough batter reacts with the baking soda and leavens the dough, while softening the starter’s sourness. Cook baking-soda batter without letting it rest, because the reaction starts right away. Discard can also be added to bread dough along with commercial yeast for flavor. If it is the only leavener in a loaf of bread, the dough will not reach its expected volume and will turn out heavy and dense; use it only as an additional ingredient.

Discard can be collected in the refrigerator in a covered container that is not sealed airtight, to prevent gas buildup; how long it keeps is a separate storage question. The saved discard contains the flour and water from the feeding, so count those toward the recipe and reduce its liquid accordingly. A thin layer of liquid with a dark color and sharp smell may collect on starter that has been stored for a long time; it may indicate a need for feeding. Discard the entire starter if it has mold, a pink or orange color, or an unpleasant smell unlike its usual sour or alcoholic odor.

Use the same criteria for discard as for the starter itself. A healthy starter smells tangy and slightly fruity; a darkened starter without mold is simply hungry. If you see fuzzy mold, pink or orange spots or streaks in the jar or discard, or smell a sharp solvent-like or rotten odor, the starter and its discard must not be used. Do not taste them; discard everything and wash the jar thoroughly. Since the discard comes from the main starter, it shares any defect found in that starter.