Understanding Kahm Yeast in Fermentation

Kahm yeast is a surface-fermentation byproduct. It appears as a white, filmy layer atop fermenting foods, commonly mistaken for mold but is usually harmless.

Kahm yeast is distinguishable by its thin, waxy, and flat appearance. Unlike mold, it doesn't penetrate deep into food and lacks mold's fuzzy texture.

Thriving in oxygen-rich surfaces, kahm yeast predominantly forms on fermenting vegetables, fruits, and dairy. Proper submersion and anaerobic conditions discourage its growth.

While non-toxic, kahm yeast can impart off-flavors and odors to ferments. It's a sign of excessive oxygen and may indicate the need for better fermentation practices.

Prevention strategies include minimizing oxygen exposure using airlocks, maintaining clean environments, and keeping ferments at appropriate temperatures to favor beneficial bacteria over kahm yeast.

If kahm yeast appears, simply skim it off. Ensure the remaining ferment hasn't soured. A taste test can determine if the batch is salvageable.

In brewing, kahm yeast is an unwelcome contaminant. It can ruin batches of beer, wine, or kombucha by creating off-flavors and compromising the intended yeast culture's performance.