What sign indicates that a beer may not be servable?

A sign that a beer may not be servable is the presence of white flakes in the beer. These flakes can indicate a problem with the beer, such as contamination or poor filtration, leading to unwanted sedimentation or spoilage. The presence of particles can negatively affect the beer's flavor, aroma, and overall drinkability, making it unappealing to consumers.

While a clear appearance typically suggests that the beer is properly filtered and free from unwanted particles, sharp tastes can sometimes be characteristic of certain beer styles or ingredients. Thick foam can also be normal depending on the beer type and serving method. However, white flakes are a clear signal that something is off with the beer, warranting closer inspection before serving.