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Looking into individual coffee beans during the roasting process: Direct micro-probe sampling on-line photo-ionisation mass spectrometric analysis of coffee roasting gases.
Anal. Bioanal. Chem. 405, 7083-7096 (2013)
A micro-probe (μ-probe) gas sampling device for on-line analysis of gases evolving in confined, small objects by single-photon ionisation time-of-flight mass spectrometry (SPI-TOFMS) was developed. The technique is applied for the first time in a feasibility study to record the formation of volatile and flavour compounds during the roasting process within (inside) or in the direct vicinity (outside) of individual coffee beans. A real-time on-line analysis of evolving volatile and semi-volatile organic compounds (VOC and SVOC) as they are formed under the mild pyrolytic conditions of the roasting process was performed. The soft-ionisation mass spectra depict a molecular ion signature, which is well corresponding with the existing knowledge of coffee roasting and evolving compounds. Additionally, thereby it is possible to discriminate between Coffea arabica (Arabica) and Coffea canephora (Robusta). The recognized differences in the roasting gas profiles reflect the differences in the precursor composition of the coffee cultivars very well. Furthermore, a well-known set of marker compounds for Arabica and Robusta, namely the lipids kahweol and cafestol (detected in their dehydrated form at m/z 296 and m/z 298, respectively) were observed. If the variation in time of different compounds is observed, distinctly different evolution behaviours were detected. Here, phenol (m/z 94) and caffeine (m/z 194) are exemplary chosen, whereas phenol shows very sharp emission peaks, caffeine do not have this highly transient behaviour. Finally, the changes of the chemical signature as a function of the roasting time, the influence of sampling position (inside, outside) and cultivar (Arabica, Robusta) is investigated by multivariate statistics (PCA). In summary, this pilot study demonstrates the high potential of the measurement technique to enhance the fundamental knowledge of the formation processes of volatile and semi-volatile flavour compounds inside the individual coffee bean.
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Publication type
Article: Journal article
Document type
Scientific Article
Keywords
Coffee bean; Roasting; Micro-probe sampling; Single-photon ionisation mass spectrometry; Volatile Organic-compounds ; Single-photon Ionization ; Robusta Coffee ; Espresso Coffee ; Raman-spectroscopy ; Component Analysis ; Aroma Compounds ; Green Arabica ; Headspace ; Discrimination
Language
english
Publication Year
2013
HGF-reported in Year
2013
ISSN (print) / ISBN
1618-2642
e-ISSN
1618-2650
Quellenangaben
Volume: 405,
Issue: 22,
Pages: 7083-7096
Publisher
Springer
Publishing Place
Heidelberg
Reviewing status
Peer reviewed
POF-Topic(s)
30202 - Environmental Health
Research field(s)
Environmental Sciences
PSP Element(s)
G-504500-001
PubMed ID
23657458
WOS ID
WOS:000323651900021
Scopus ID
84883459834
Erfassungsdatum
2013-07-31