It can happen.

Natural Leavening Yeast Sourdough Mold? Ask Amy

Dear Amy,

Hey, quick questionwill the [Natural Leavening yeast] sourdough mold? My starter turned dark and formed a liquid on top. I thought I killed it. I’m paranoid. Thanks, Emilie M., Provo, UT.

Afraid of Mold. When I first began natural leavening, I was afraid of mold growth. Each week, I would carefully check my bowl of beneficial bacteria for invaders of the fuzzy, furry kind. Common practice discourages leaving food in the danger zone, 40-140’F, for more than 4 hours. Culturing requires leaving grain at room temperature for an extended period of time. The potential of mold can definitely scare the fermenting novice, because you don’t know what is normal.

Natural Discoloration.

Pour off the hooch, it won't hurt you.

Natural Leavening Starter Hooch. Starter may discolor and turn dark or form “hooch” liquid separation on top. Simply scrape off discoloration or pour off any liquid. Refresh with flour and water.

Darkening may occur over a few days with exposure to oxygen, even when the starter is covered in the fridge. You’ve seen a similar, but faster, reaction with cut apples and bananas. This browning will not harm anyone. Just like the fruit, the Natural Leavening browns on the surface that is exposed to the air. You can scrape this portion off before you refresh the Leavening, for appearance sake.

Liquid separation, called hooch, may form on top of spent, flattened, compressed, spent Leavening. This is a normal progression for unrefreshed, “hungry” Leavening. Simply pour off the liquid, scrape off discoloration if desired, and refresh with flour and water.

No Mold Here. Dr. Dough and I have been fermenting for a while now, since 2006. Our youngest three children have only seen naturally leavened bread in our home. We’ve never been sick from ferments or food contamination. We’re in our eighth year and we’ve hardly seen mold. We followed some rules for safe food handling and culturing and recommend them to you.

Safe Food Culturing Guidelines:

  1. Begin with a sterilized jar, lid, and spoon.
  2. Wash hands thoroughly before handling any food including grain, flour, starter, and water.
  3. Use, refresh, or refrigerate cultured starter. If you don’t use it, refresh it, or refrigerate it, you’re apt to grow mold at the top of your covered container.
  4. Throw out moldy looking starter. Do not use, eat, refresh, or cook with it. Sterilize the container in HOT 180’F water. Start over with dry Natural Leavening starter.

Mold Appearance.

It can happen.

Natural Yeast Leavening Sourdough Mold. Gross! Fuzzy and hairy, beware of mold when you see it in any color. Throw mold out. Avoid mold with safe food handling and culturing guidelines.

I have seen moldy starter a few times on various types of grain–rice, quinoa, hard white wheat. I imagine any wet grain starter, deprived of oxygen and refreshment may mold. I’ve seen white, turquoise (pictured), yellow-orange, and black mold on a starter. Each time the mold presented in a fuzzy, hairy manner. Throw mold out!

Mold Development. Mold develops in moist environments. The starters that molded were left at room temperature with the lid on and not refreshed or used. The poor starter remains were forgotten and sealed in a jar, with no food or water. Sounds inhumane? It was the death of the above mentioned starters.

Sincerely, Amy, R.D.

p.s. Sorry, no recipe this week. This question was so unappetizing.

Did your Natural Leavening, yeast, or sourdough starter mold? Don’t worry, we can share.

Amy McClean, registered dietitian, and Dr. Matthew McClean, “Dr. Dough” have not purchased a loaf of bread since 2006! At the time of this writing, all proceeds from the sale of Natural Leavening starters and classes have been put back in to natural leavening research and education.


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