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

Draft lines that are not cleaned regularly can lead to the growth of bacteria and wild yeast, which may produce off-flavors in the beer. The presence of vinegar flavor is typically associated with acetic acid, which can develop from improper hygiene practices in the serving system. When draft lines are neglected, organic material and residue from previous beers can build up, providing a conducive environment for these microorganisms. It is this buildup that can contribute to sour or vinegary flavors, making vinegar the most likely flavor to develop.

In contrast, flavors like butter, metallic, or dusty are linked to different causes such as diacetyl (butter), oxidation or contamination from metals (metallic), or environmental factors (dusty) rather than a lack of cleanliness in the draft system. This contextual understanding of flavors helps emphasize the importance of regular maintenance and cleaning of draft lines to ensure quality beer service.