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Resonance-enhanced multiphoton ionisation time-of-flight mass spectrometry (REMPI-TOFMS) enables the fast and sensitive on-line monitoring of volatile organic compounds (VOC) formed during coffee roasting. On the one hand, REMPI-TOFMS was applied to monitor roasting gases of an industrial roaster (1500 kg/h capacity), with the aim of determining the roast degree in real-time from the transient chemical signature of VOCs. On the other hand, a previously developed μ-probe sampling device was used to analyse roasting gases from individual coffee beans. The aim was to explore fundamental processes at the individual bean level and link these to phenomena at the batch level. The pioneering single-bean experiments were conducted in two configurations: (1) VOCs formed inside a bean were sampled in situ, i.e. via a drilled μ-hole, from the interior, using a μ-probe (inside). (2) VOCs were sampled on-line in close vicinity of a single coffee bean's surface (outside). The focus was on VOCs originating from hydrolysis and pyrolytic degradation of chlorogenic acids, like feruloyl quinic acid and caffeoyl quinic acid. The single bean experiments revealed interesting phenomena. First, differences in time-intensity profiles between inside versus outside (time shift of maximum) were observed and tentatively linked to the permeability of the bean's cell walls material. Second, sharp bursts of some VOCs were observed, while others did exhibit smooth release curves. It is believed that these reflect a direct observation of bean popping during roasting. Finally, discrimination between Coffea arabica and Coffea canephora was demonstrated based on high-mass volatile markers, exclusively present in spectra of Coffea arabica. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Coffee is for most us a morning priority to efficiently kick‐start our day. Coffee beans contain small concentrations of volatile and semi‐volatile organic compounds. When coffee is roasted, complex chemical and physical processes occur, which result in the formation of browning pigments and (oh so pleasant and pleasing) flavor compounds. Over 500 distinct compounds can be identified, however, despite extensive research on coffee flavor formation; the knowledge about these processes remains fragmentary. In this perspective special feature article, Dr. Ralf Zimmermann and colleagues demonstrate the online analysis of coffee volatile organic compounds formed during the roasting process by resonance‐enhanced multiphoton ionization time‐of‐flight mass spectrometry (REMPI‐TOF MS). Aromas issues from large‐scale batch and individually roasted beans are compared. Dr. Ralf Zimmermann is professor of analytical chemistry at the University of Rostock (Germany). His main research interests are in the development of new methods and technologies of mass spectrometry and modern chromatographic separation techniques. [ABSTRACT FROM AUTHOR]