Coffea liberica presents the smallest proportion of cultivated coffee worldwide. Its taste varies highly from C. arabica spp. or C. canephora spp. As the unfermented taste of C. liberica is often described as lactic, and animalic with aromatics of blue cheese, fermentation experiments of C. liberica coffee cherries were conducted. Coffee cherry fermentation is carried out to modify and enhance the sensory profile of green and roasted coffee beans. Various microorganisms change the composition of organic precursor compounds, reducing off-flavours during green bean coffee processing and roasting. For the comparison of the sensory properties of fermented coffee beans, SCA-trained experts grade the coffees by specific sensory attributes. Roasted and ground coffee powder, as well as ground raw coffee samples, were analysed by headspace-gas chromatography–mass spectrometry/ion mobility spectrometry (GC-MS/IMS) to determine the volatile fingerprint of unfermented and fermented C. liberica coffee. Eight different unfermented C. liberica samples were analysed and the volatile profiles compared to those of arabica spp. and canephora spp. The unfermented coffee beans differ in origin and processing. Furthermore, single-origin C. liberica fermented with two different wine yeasts was compared to unfermented C. liberica. The fermented coffee beans share the same variety, processing, and profile of roasting and differ only in their origin and fermentation inoculum. This study presents the direct comparison of the aromatic fingerprint measured in the instrument. Compound regions in the spectra associated with different coffee species and ferments are shown. The potential of GC-IMS for fast comparison of the aromatic fingerprint is demonstrated.

Proceedings: Kiefer, C.; Schwarz, S.; Rohn, S.; Weller, P. The Aromatic Fingerprint of Fermented Coffea liberica . Proceedings 2023, 89, 4. https://doi.org/10.3390/ICC2023-14838