Prevention and Treatment of Kahm Yeast

by Jerri

Recently, I wrote a pretty general post about kahm yeast. It's been a few weeks with my fermentation project, and here's what I have on my counter now: 

kahm yeast appearing at the top of fermenting vegetables

The jar in the middle has the culprit on top, but all three jars have the same hot peppers and the same brine concentration, as well as their fermentation spot is the same granite countertop.

I still think it's weirdly beautiful, but after more research online about how other avid fermenters wage their war with this harmless yeast, here's what was found to help YOU win the war, or at least suture the wounds:  

Preventing Kahm Yeast:  

  • Ferment in cooler room temps, 70º and below - if you think about the olden days, fermenting was traditionally done in unfinished basements, root cellars, or buried underground. All of these places can be near 55º or so! Even if yeast doesn't form, you will likely get mushy or moldy veggies, or they will taste off (or just plain gross) at 70º or above.
  • Clean all tools and vessels well - use boiling water/white vinegar to really get them clean sans chemicals, rinse with hot water, and finally cool everything before using in your ferment.
  • Use a higher concentration of salt in the brine, but not over the 3 Tbs salt per 1 quart water ratio (too much salt stops fermentation)
  • Chop food into smaller pieces for more surface area and thus availability of natural sugars; this gets the acidity level lower faster so yeast can't form!
  • If you have larger pieces of food or expect to ferment a longer time, use more salt. Yes, it will be salty.
  • Keep it all submerged under the brine! If kahm yeast does form, it will form on the surface (but work its way down), and you can skim it off much easier.
  • Keep as much oxygen out as possible. This means fill the container to at least 80% so you have at least 1" of headspace. This also means, if you have had kahm yeast in the past, try to refrain from opening the container too often unless you really, really need to burp it to prevent an explosion. 
  • Use airlocks = less chance of kahm yeast (and mold)  

After Kahm Yeast to soothe those battle wounds, you can remove the yeast and then:   

  • Sprinkle some salt on top of the surface
  • Add more brine that has a larger salt concentration
  • Remove and clean weights well: soak in vinegar, rinse in hot water, allow to cool before putting back in the jar
  • Move to a cooler spot, well below 70º
  • If you had yeast form even though using an airlock system, this is normal, but it may be that your lid is still allowing oxygen to get in. If you do more ferments down the road that keep yielding yeast no matter what you try, it's probably time for a new lid/seal. I believe this was my issue with the 1 of 3 jars that developed that lovely layer!
  • If you don't have much yeast forming, you can stir it back in
  • Try to remove as much kahm yeast as you can, but even Sandor Katz says eating it won't hurt you. If you continue to ferment the same jar, it likely will keep coming back, so as Dory in Finding Nemo would sing, "Just keep skimming, just keep skimming, just keep skimming, skimming, skimming, what do we do...we skim, skim". That is what she was singing, wasn't it?