Jar of sourdough starter with slices of bread on the side
Your Sourdough Starter Has Gone Bad If You Notice These Red Flags
To know whether or not your sourdough starter is salvageable, first look for signs of mold. Any orange, pink, blue, or green spots on the container or starter are definite signs.
Even if you don’t see any signs, sniff your starter before using it. If it has an unpleasant smell that's stronger than the typical sharp and sour scent, it’s best to start over.
If it’s been a while since you fed your starter, you may notice a layer of liquid on top called hooch, which can range from clear to black but isn’t a sign to scrap the batch.
In reality, it’s hard to ruin a sourdough starter. If you notice it’s been neglected, simply feed it vigorously a few times to bring it back to life before using it.