Identification of Compounds that Negatively Impact Coffee Quality Using Untargeted LC/MS Analysis.

Untargeted Liquid Chromatography/Mass Spectrometry (LC/MS) flavoromics analysis was carried out on 18 coffee brews ranging in Specialty Coffee Association (SCA) cup scores. Six compounds highly predictive of low cup score were isolated from coffee using multi-dimensional preparative LC/MS and further evaluated by sensory recombination analysis with certified SCA Q-graders. A significant decrease in cup score was demonstrated with four out of the six compounds when added to a specialty coffee brew. High-resolution MS, mono- and bidimensional nuclear magnetic resonance (NMR) experiments were used to successfully elucidate four of the structures as 16alpha,17-dihydroxy-ent-kauran-19-oic acid (compound 1), its diglycosidic compound 16alpha,17-dihydroxy-ent-kauran-19-diglycoside (compound 2), 16alpha,17,18-trihydroxy-ent-kauran-19-oic acid (compound 5), and 16alpha-hydroxy-17-ent-kauren-19-oic acid (compounds 6). All four ent-kaurane diterpene compounds were endogenous to green coffee beans providing direct chemical indicators of low-quality coffee.