Are you having problems with your sourdough starter? Are you wondering how to keep sourdough starter from molding? Use this comprehensive guide to understand what’s happening with the microbial community in your sourdough starter and learn how to fix the most common sourdough starter problems.
What Microbes are in Sourdough Starters?
Many types of microbial fermentation happen simultaneously in healthy starters. It is a mixed type of fermentation because starters consist of a rich, wild, mixed culture of yeast and bacteria. When you culture a sourdough starter, wild yeasts metabolize wheat sugars and carbohydrates into alcohol. At the same time, bacteria consume the sugars, alcohol, and starches in the starter to produce acids. The bacteria can metabolize carbohydrates from the flour into acids. They can also convert the yeast-produced alcohol into acetaldehyde and acetic acid. The rise and bubbles come from the wild yeast, and the rich sour flavor comes from the bacteria.
How to Make a Sourdough Starter
It’s simple to make a sourdough starter at home; you only need flour and water! I prefer to feed my sourdough starter sprouted rye flour, but organic bread flour works well too.
- Click here to learn how to make a sourdough starter with bread flour
- Click here to learn how to make a sourdough starter with sprouted rye flour
Getting a sourdough starter established is even easier if you can begin with a starter from someone else. I am selling my sprouted rye sourdough starter, Reuben, here.
How to Keep Sourdough Starter from Molding
It’s easy to keep your sourdough starter from molding. Just follow these three rules:
- Discard and feed your starter fresh flour and water every 24 hours. Do not skip any feedings. If you need to skip a feeding, put your starter in the fridge.
- Feed your starter in a clean jar. Move your starter to a fresh, appropriately sized, clean jar every other day.
- Use the right flour to water ratio. For bread flour starters use 1:1, for most whole wheat and rye flours use 1:2.
The best way to keep your sourdough starter from molding is to feed it often enough. You must discard sourdough starters and feed them fresh water and flour every 24 hours minimum. It’s always a good idea to move your starter to a fresh, appropriately sized, clean jar at least every third day. I move my starter to a clean jar daily.
Usually, mold destroys any ferment. However, sourdough starters are the most forgiving of any fermented food. White mold or fungus can grow as a pellicle on the surface of your starter for three main reasons. First, mold can grow when you do not discard and feed your starter often enough. Second, you may encounter mold problems if you don’t switch to a clean jar often enough. Third, if there is a lot of air space in the jar, the top of the starter can dry out and cause a pellicle to grow.
If you experience what looks like mold on your starter, just carefully remove the pellicle and all the fungal growth you can. There should be a bit of unscathed sourdough starter underneath. Then, using a clean utensil, grab a small amount of untainted starter that was not near the mold and add it to a new jar. Then discard and feed as usual.
If there is black, blue, or green growth that is fuzzy, you should throw it away and start over. Next time, make sure you feed your starter within 24 hours. If you cannot feed your starter within 24 hours, place it in the fridge for hibernation.
What if My Sourdough Starter Smells Like Alcohol?
Are you asking yourself “why does my sourdough starter smell so bad?” The answer depends on the type of smell.
Don’t freak out if you smell strange smells like alcohol or acetone. These sourdough starter smells are quite normal and interesting! This smell means that the bacteria in your starter need more oxygen to finish converting yeast-produced alcohol into acetic acid. If there isn’t enough oxygen, the bacteria get stuck in the middle of the conversion process, with a build of acetaldehyde (which smells like nail polish). Once you expose them to more oxygen by stirring, discarding, and feeding, they can finish converting acetaldehyde into acetic acid. It’s simply the smell of bacteria converting alcohol to acids for flavor! You can also put your starter near a fan, maybe a houseplant, or an open window on a cool day for more air circulation.
What Should a Sourdough Starter Smell Like?
A healthy sourdough starter should smell sour like vinegar and yeasty like beer. The smell should be pleasant but brightly sour. Any off or repulsive smells are usually because of poor feeding practices, or from feeding with poor quality flour. Make sure you are using high-quality organic flour to feed your sourdough starter.
My Sourdough Starter has Liquid on Top
If you see liquid on the top of your sourdough starter, do not be alarmed. This is normal and no big deal. If you find a liquid layer on the top, it could be alcohol produced by yeast, or it could mean your starter is simply too watery. This is a common problem when using white flour, like bread flour or all-purpose to grow and feed a starter. When using rye or whole wheat flour more water is absorbed when compared to using bread flour or all-purpose.
The germ and bran that are present in whole wheat flour can absorb more liquid; white flours lack the germ and bran and only contain the endosperm which does not absorb as much water. If your starter has watery separation, pour the liquid off, discard 3/4 of the starter, then feed it with equal parts water and flour. It’s best to discard and feed your starter with a 1:1:1 starter to flour to water ratio. Try using thicker flour like whole wheat or rye.
If you are not using rye flour, and you notice a more prominent pink discoloration in your starter or on the surface of your starter, you need to throw it out and start over. The discoloration is most likely from Serratia marcescens, an undesirable bacteria often found in pipes and tap water.
If you use 100% rye flour to feed your starter, sometimes your starter can take on a soft reddish tone.
Purple Discolored liquid
Purple-hued liquid on the sourdough starter is called “Hooch,” which is alcohol. It accumulates on the surface of your starter when you do not feed it enough. Hooch is most commonly clear, beige, brown, purple, gray, and black. The color depends on the flour and the unique microbes present. Hooch is just the alcohol given off as wild yeasts ferment wheat. Don’t worry if you have a discolored liquid layer in your starter jar. It is not a sign that your starter is dying. However, it does indicate that your starter is hungry and needs to be fed. Just pour off all the liquid, discard 3/4 of the starter, then feed.
Refrigerating and Reviving Your Sourdough Starter
If you’ve used some of your sourdough starter to bake, and you do not plan on using your starter again anytime soon, you can hibernate it.
- In a clean jar add:
- 50 grams starter mixture ( 4 Tablespoons )
- 75 grams of flour (if using whole wheat or rye, use less flour here)
- 75 milliliters filtered water
- Stir until evenly combined, and scrape down the sides of the jar.
- Let it sit at room temp until bubbly, then close with a solid lid and place in your refrigerator.
- Feed starter every 2 weeks. (note that starters can be neglected in the fridge and still be revived. It’s okay if you leave it longer than two weeks without feeding.)
- Reviving sourdough starter from fridge: move to room temperature and continue to discard and feed every 24 hours.
Why is My Sourdough Starter Not Bubbling?
Of all the sourdough starter problems, this is the most common. You may be wondering if your sourdough starter is dead simply because it is not bubbling. If you feel like your sourdough starter is not bubbly and rising enough, here’s what you can do:
Starters can be quite soft and wet. If you are at work all day or sleeping, you may miss it expand and rise. This is normal since it is so hydrated. If you want your starter to “hold” the rise a little longer, make the starter thicker by using a bit more flour and less water. CLICK HERE for our sourdough starter recipe.
REMEMBER: The amount of flour and water you feed your starter can vary a bit. The thing to remember is that different flours absorb different amounts of water. For rye and whole wheat starters, you need about a 1:2 ratio of flour to water for feedings (so that would be 50 grams flour 100 grams water). For white bread flour and all-purpose flour, you need a 1:1 ratio of flour to water (so 50 grams flour 50 grams water) for feedings. If you notice early watery separation, just add an extra spoonful of flour.
Try more complex flours
Try feeding your starter a mix of heirloom flours from somewhere like Lindley Mills. I like a mix of rye, spelt, and buckwheat when I feel like my starter needs a boost. You can also try feeding your starter sprouted flours, like sprouted Enkinhorn, sprouted spelt, or sprouted rye. These types of flours absorb more water, so will give you a thicker starter that can hold a rise longer.
Add in some fermented vegetable brine
Wild Sourdough yeasts benefit from the presence of bacteria and vice versa. So adding a little bit of sauerkraut brine in at the beginning just speeds up the formation of this awesome microbial relationship. I use fermented vegetable brine to make starters all the time. My starter, Reuben, was originally started with fermented vegetable brine that is now 2.5 years old. I find the flavor to be more developed and rich with my brine starters, and I prefer it. My loaves come out beautiful, too.
How Long do Sourdough Starters Take to Rise?
I feel like timelapse videos of starters rising have confused people on sourdough starter timelines. Your starter will not rise on your watch, it really depends on feed frequency and temperature. After feeding, a sourdough starter can take anywhere from 5-24 hours to bubble up and rise. Be patient with it; you may need to wait for the bubbly rise, or it might happen while you’re sleeping. Also, your sourdough starter may not look like the pictures here, if it’s bubbling and has expanded, you can use it to bake.
Most of the wild yeasts in sourdough starters originate from the flour used to make the starter. Those yeasts originated in the soil in which the wheat was grown. Therefore, You’ll get the most species-rich starter by using a mix of organic flours plus a little wild fermented sauerkraut brine.
Did I Kill My Sourdough Starter?
It’s quite hard to kill a sourdough starter. Even the most neglected starters can often be brought back to optimal activity. I think it’s important that we go over a few things that have no effect on your starter and definitely will not kill it:
- Metal spoons: This is a ridiculous claim. While you shouldn’t store it in a metal container for long periods of time, you can totally stir it with a metal spoon. Stirring with a metal utensil does not change anything about your starter.
- Inaccurate flour measurements when feeding: The amount of flour and water you feed your starter can vary a bit. The thing to remember is that different flours absorb different amounts of water. For rye and whole wheat starters, you need about a 1:2 ratio of flour to water for feedings (so that would be 50 grams flour 100 grams water). For white bread flour and all-purpose flour, you need about a 1:1 ratio of flour to water (so 50 grams flour 50 grams water) for feedings.
- Refrigeration: Yes, you can store your starter in the fridge. As long as you still discard and feed every 1-2 weeks, it’ll be easy to start back up. This is a great way to reduce discard and flour consumption if you’re taking a break from baking. Honestly, I’ve neglected a starter in the fridge without feeding for 2 months, and it still came back to life with the first feeding.
Generally, sourdough starters will only die from severe neglect. Keep it between 70-80 degrees, keep it out of direct sunlight, discard and feed every 24 hours, take care of any issues that arise in a timely manner and you won’t kill it.
Reviving Dehydrated Sourdough Starter
Still can’t get your starter to cooperate? I suggest buying some dehydrated starter from a quality baker and starting with that. I sell My 100% organic sprouted rye sourdough starter, Reuben, on our online store. Ruben is a 100% sprouted rye wild sourdough starter grown with Cultured Guru Wild Fermented Sauerkraut Brine, Lindley Mills organic sprouted rye flour, and water. It comes with 10 grams of dehydrated sourdough starter fresh from my home kitchen. Rehydrating is simple, with just flour and water. I include a full instruction sheet with the starter and the rehydrating process requires a kitchen scale.
Sourdough recipes to try with your starter
- Customizable Sourdough Focaccia Bread From Scratch
- The Best and Easiest Gluten-Free Sourdough Bread
- Easy Homemade Sourdough Pizza Crust
- How to Bake Sourdough Discard Banana Nut Muffins