Sourdough starter that is stored in the fridge for a long time can develop a very dark colored hooch that is often mistaken for mold. Similarly, if left on the counter, some starters can develop darker patches that may look like mold forming. It is actually the very beginnings of hooch.
A. The dark liquid is a form of naturally occurring alcohol known as hooch, which indicates that your sourdough starter is hungry. Hooch is harmless but should be poured off and discarded prior to stirring and feeding your starter.
Mold can appear in various colors and is typically fuzzy in appearance. Bad bacteria is generally indicated by an orange or pink tinge or streak. Once your starter has lost its natural ability to ward off intruders, it's time to start over.
The most common separation you'll in a sourdough starter is when you get black or gray liquid on top. This is completely normal. The black liquid on top of your starter is called hooch. Hooch is the waste product of the sourdough starter.
Liquid on Top of Sourdough Starter
This is a layer of clear, black, or brown liquid that forms on top which is an alcohol that's produced from the yeast growth. Hooch is actually edible, so you can mix this in with the starter, or pour it off and feed it as normal. Either way, your starter isn't bad when it has hooch.
Signs of a Bad Sourdough Starter
If your starter has mold growing throughout it (not just a little on top), or if it smells really foul (not just super sour), or if it turns an odd color (not just gray, which is normal, but pink or green), it may be time to start over.
Dough that is over-fermented will start to spread once scored and look bubbly/weak. You'll notice it falling in a bit or a lot. Notice how the whole loaf is collapsing. If you notice your dough is over-fermented be sure to score very shallow and use a minimum of scoring slashes.
Remove the mold from the surface. Using a clean utensil, remove a small portion of the sourdough that wasn't near the mold. A tablespoon will suffice. Put that tablespoon in a clean container, and feed using the ratio of one part starter to one part water to a scant two parts flour.
If your sourdough starter is obviously moldy, then unfortunately the starter has gone bad and should no longer be used. Mold on sourdough starter will look raised and fuzzy, and can range in color from white, yellow, green, blue or pink spots.
Typically you can begin to give up at around day 5-7. (Especially if you've taken an aggressive feeding schedule.) With an aggressive feeding schedule (2-3 times daily), you should begin to see bubbling and sour notes by day three (and is a good indicator for collecting the Lactobacillus bacteria).
There is a black liquid sitting on top of your sourdough and you are wondering what to do with it. This black liquid (hooch) is actually normal and doesn't necessarily mean your starter has gone bad. If there is no mold or orange/pink streaks in the sourdough starter, it is still ok to use.
It does, however, mean your starter needs to be fed–the sooner, the better. You can pour off the hooch or mix it back in. If your starter is getting hooch on a regular basis, you need to adjust your feeding schedule. This may be especially true for warmer months.
Kahm yeast sometimes floats over the layer of alcohol that separates out of your starter if the time between feedings is much too long. Kahm yeast isn't harmful. If your starter develops a layer of it, you can just scrape that layer off, transfer the remainder of your starter to a clean jar and feed it.
Because, yes, you can overfeed your sourdough. The explanation is quite simple: if you add too much water and flour, you're basically diluting the natural population of yeast and bacteria. This means that your sourdough starter will not rise much and will not be very bubbly.
The rule of any kitchen is “When in doubt, throw it out,” but I wouldn't panic and toss your starter if you only missed 1-3 days of feeding. If it's more than 3 days AND you have a warm kitchen, you'll have to make the call based on how well you know your starter.
The discard is just the sourdough starter you're not currently feeding or baking with. It's called discard because it often gets "discarded" during feeding. If you don't "discard" some starter during feeding your starter will just grow and grow and grow until you're staring in a remake of The Blob.
Troubleshooting: Contaminated starter should be discarded. Sourdough starter that shows any sign of mold (colored and/or fuzzy) should NOT be used, and the container should be thoroughly cleaned and rinsed before starting over. Sourdough starter may develop a liquid layer that smells of alcohol, and this is fine.
Cleaning a sourdough starter jar can be tricky if it's very caked on. Soak the jar in cold water and use a dough scraper or knife to scrape off any build up. Wash the jar thoroughly in warm soapy water once the excess has been removed or place into the dishwasher. You don't have to sterilize sourdough starter jars.
Ideally, you don't want to allow sourdough bread to cold ferment for longer than 72 hours. Even up to 48 hours, you do risk some loss of gluten structure unless you manipulate the amount of starter down.
Step 1: Perform the fingertip test to make sure your dough is overproofed. The test involves gently pressing your finger into the surface of the dough for 2 seconds and then seeing how quickly it springs back. The dent you make will be permanent if the dough is overproofed.
Overproofed is when the dough has rested too long and the yeast has continued making carbon dioxide while the strength of the dough (gluten bonds) have begun to wear out. The dough will look very puffy, but when you touch it or move it you may notice it deflate or sag.
As part of the feeding process, most bakers discard some of their sourdough starter before adding fresh flour and water to the jar. This is done to refresh the acidity levels (think sweet vs. sour smell) and to manage its overall growth in size. This technique is crucial for successful sourdough bread.
The main difference between kahm yeast and mold is that mold will look fuzzy, while kahm yeast is white and matte and tends to cover the entire surface of a ferment.
Kahm yeast is actually safe to eat as long as there are no molds present and the ferment tests at a pH of 4 or lower. Kahm yeast however can cause a disagreeable flavor or aroma. If your ferment does not smell pleasing to you it will most likely not get eaten so disposing of it in the compost might be the best bet.
Kahm yeast is a thin, white to cream-colored layer, sometimes with air bubbles of trapped carbon dioxide. It often has a “stringy,” bloom-like look to it. Mold, on the other hand, is raised and fuzzy and can be white, black, pink, green or blue.