Kahm or Kahm yeast is a layer of wild yeast which sometimes is formed on fermented foods such as sauerkraut. It is typically harmless but the smell and appearance tends to spoil the food. The yeast genera which form these films include Debaryomyces, Mycoderma and Pichia.
The word âÂÂkahmâ traces back to the Middle High German âÂÂkanâ which in turn derives from the Vulgar Latin âÂÂcanaâ (greyish layer of dirt on wine).