The origin of the batch-to-batch inconsistency in flavor of Purgatory Beer Company's Fiero Coconut Rum porter was investigated by extracting organic compounds from desirable and undesirable batches of porter and quantifying them using GC-MS. The concentration and occurrence of key flavor compounds were compared between the samples and showed that the undesirable batch contained more unpleasant organoleptic compounds and was more acidic. Based on the marked inconsistency in chemical profile between batches, the team recommended quality control be improved through more accurate monitoring and consistent control of the fermentation temperature, oxygenation of wort and beer, order of ingredient addition to the fermentation broth, reuse of yeast, and filtration of water
