If draft lines are not cleaned regularly, which of the following flavors is most likely to develop?

When draft lines are not cleaned regularly, the buildup of organic matter such as yeast, bacteria, and residual beer can lead to off-flavors in the beer dispensed from those lines. A common undesirable flavor that can develop from this accumulation is vinegar, which is associated with acetic acid production. This can occur when certain types of bacteria are allowed to flourish in the unclean lines, particularly acetobacter, which converts ethanol into acetic acid, resulting in a vinegar-like taste.

Maintaining clean draft lines is crucial to ensuring that the beer remains fresh and free from these off-flavors, as clean lines will prevent the growth of harmful microorganisms and preserve the intended flavors of the beer. In contrast, while flavors such as butter, metallic, or cardboard can stem from other issues related to beer handling and storage, the likelihood of vinegar developing specifically relates to poor sanitation practices in draft systems.