If draft lines are not cleaned regularly, which flavor is most likely to develop?

When draft lines are not cleaned regularly, a flavor often associated with the beer produced is butter. This undesirable flavor is primarily the result of diacetyl, a compound produced by yeast during fermentation. If beer is left sitting in dirty lines, bacteria can also contribute to off-flavors, which may include those reminiscent of butter.

Diacetyl has a buttery aroma and flavor, and while it can also arise from the yeast itself, improper handling and lack of cleanliness can lead to increased concentrations of the compound in the final beverage. Regularly cleaning draft lines is crucial to maintaining the quality and flavor of the beer served, helping to prevent the development of diacetyl and ensuring that the beer tastes as intended.

The other flavors mentioned, such as banana, paper, and skunk, are associated with different causes—like certain yeast strains, oxidation, or light exposure, respectively—but they are not directly linked to the failure to clean draft lines. This makes the butter flavor the most likely outcome of neglecting draft line sanitation.