Study of composition of espresso coffee prepared from various roast degrees of Coffea arabica L. coffee beans

Espresso coffee samples prepared at various roasting degrees defined according to its basic conventional classification (light, medium, medium-dark and dark roasted) were analyzed by ultra-performance liquid chromatography/tandem mass spectrometry. Obtained raw data were processed using multivariate statistical analysis (Principal Component Analysis, PCA) to evaluate chemical differences between each roasting degrees (untargeted part of study). All four roasting degrees were resolved in appropriate Score plot. Orthogonal Projections to Latent Structures provided signals of significant markers describing the differences among particular roasting degrees. Detailed interpretation of those signals by targeted LC/MS2 analysis revealed four groups of compounds. The first two groups involve chlorogenic acids and related lactones. The signals of other two sets of markers were ascribed to some specific atractylosides and particular melanoidins. Ratios of contents of selected representatives of each group to the sum of all identified markers were proposed as definite parameters for determination of roasting degree of Brazilian coffee Arabica.