What does the term "Krausen" refer to in brewing?

The term "Krausen" refers to the frothy head that forms on top of fermenting beer. During fermentation, yeast becomes very active and produces a combination of foam and bubbles as it consumes sugars and releases carbon dioxide. This foamy layer typically appears shortly after fermentation has begun and can be quite thick, often rising above the surface of the beer in the fermentation vessel.

Krausen is an important visual indicator of fermentation activity and can vary in appearance and duration depending on the yeast strain, fermentation temperature, and the specific beer recipe being used. It's a critical component in the brewing process as it signifies that yeast is healthy and actively fermenting the wort. This phase of fermentation can also affect the flavor profile and overall quality of the finished beer.

In conclusion, recognizing and understanding krausen can help brewers assess the fermentation process and make necessary adjustments if the krausen does not develop as expected.