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Application of Laser Ionization Mass Spectrometry for On‐line Monitoring of Volatiles in the Headspace of Food Products: Roasting and Brewing of Coffee
Author(s) -
Zimmermann Ralf,
Heger Hans Jörg,
Yeretzian Chahan,
Nagel Holger,
Boesl Ulrich
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(199612)10:15<1975::aid-rcm786>3.0.co;2-x
Subject(s) - chemistry , roasting , mass spectrometry , ionization , time of flight mass spectrometry , analytical chemistry (journal) , chromatography , ion , organic chemistry
Resonance‐enhanced multi‐photon ionization time‐of‐flight mass spectrometry (REMPI/TOFMS) has been applied to the detection of volatiles in the headspace of brewed coffee and in the coffee roasting process‐gas. A frequency quadrupled Nd:YAG laser (266 nm) was used for REMPI ionization (REMPI@266nm) of the volatiles in an effusive molecular beam inside the ion source of a linear TOF mass spectrometer. A special sampling system provided a time correlated sampling. Under these circumstances REMPI@266nm is highly selective for ionization of phenolic compounds. Several phenolic compounds, such as the flavour‐active 4‐vinylguaiacol, can be detected in the headspace of coffee brew as well as in the roast off‐gas with the application of this approach. Moreover, the nitrogen heterocyclic compounds, indole and caffeine, were detected in both cases. During the roasting process the relative changes in concentration of some volatile components of coffee have been recorded by EMPI@266nm with a time resolution of 1 Hz. The different volatiles exhibit characteristic concentration profiles as a function of the roast time. These results demonstrate the applicability of REMPI‐TOFMS for on‐line monitoring of coffee processing technologies. Such an on‐line monitoring technique is of particular interest for process‐control purposes, e.g. quality‐protection or feedback process control. For example, monitoring of off‐gases from the coffee roast process or monitoring of certain unit operations during the instant‐coffee manufacturing could be promising industrial applications.