Smart Online Coffee Roasting Process Control: Modelling Coffee Roast Degree and Brew Antioxidant Capacity for Real-Time Prediction by Resonance-Enhanced Multi-Photon Ionization Mass Spectrometric (REMPI-TOFMS) Monitoring of Roast Gases

Abstract

Process control with high time resolution is essential to maintain high product quality in coffee roasting. However, analytical techniques for quality assurance or measurements of desired coffee properties are often labor-intensive and can only be conducted after dropping the coffee beans. Resonance-enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOFMS) at 248 nm and 266 nm was applied to analyze the composition of the roast gas from small-scale Arabica coffee roasting. Coffee beans were dropped after different roasting times, ground and analyzed by Colorette to obtain the roast degree. Additionally, the antioxidant capacity of the coffee brew was determined by Folin–Ciocalteu (FC) assay. Models for the prediction of Colorette and FC values from REMPI mass spectra were constructed by partial least squares (PLS) regression. REMPI-TOFMS enables the prediction of Colorette values with a root-mean-square error in prediction (RMSEP) below 5 for both wavelengths. FC values could be predicted using REMPI at 248 nm with an RMSEP of 80.3 gallic acid equivalents (GA-eq) mg L−1, while REMPI at 266 nm resulted in RMSEP of 151 GA-eq mg L−1. Finally, the prediction of Colorette and FC value at 5 s time resolution were demonstrated with online measurements.

Simultaneous on-line vacuum single- and multi-photon ionization on an orthogonal acceleration time-of-flight mass spectrometer platform

“…At least 250 °C are needed. Further details for the basic suitability of tofMS and photoionization for monitoring coffee roast gas can be found in the manuscripts by Heide et al 33 and Czech et al 34…”

“…The 2-in-1 approach of SPI and REMPI usage in a single measurement serves for more informational depth and is not only beneficial in environments where experiments cannot be repeated (as in industrial facilities) but, for coffee roasting, the information could also be further exploited in correlation with off-line data and model building. [33][34][35] The system is also used for such a highly dynamic process as monitoring e-cig vapor. SPI is once again used for the highly abundant analytes.…”

“…At least 250 °C are needed. Further details for the basic suitability of tofMS and photoionization for monitoring coffee roast gas can be found in the manuscripts by Heide et al 33 and Czech et al 34 In this work, the basic application of oa-tofMS with simultaneous SPI/REMPI-mode and storage in one data acquisition card shall be shown on the example of coffee roasting. Fig.…”

Vacuum Laser Photoionization inside the C-trap of an Orbitrap Mass Spectrometer: Resonance-Enhanced Multiphoton Ionization High-Resolution Mass Spectrometry

“…The corresponding detection limits ranging from 33 pg for fluorene to 196 pg for pyrene, comparable to LODs reported in the literature for routine GC-MS approaches (Table S4). − Nevertheless, instruments targeting specific compounds or tuned for ultrahigh sensitivity significantly exceed the LODs of the developed experimental system in its current form. , The use of the current instrument will be suitable in various application areas, e.g ., by targeting primary emission scenarios (wood combustion, − coffee roasting, − biomass pyrolysis, and ship emissions , ). Here, the high resolving power, spectral dynamic range, and mass accuracy of the instrument will allow additional molecular-level insights into the chemical pattern of generated PAHs, not addressable by the current ToF MS technology.…”

Hyper-fast gas chromatography and single-photon ionisation time-of-flight mass spectrometry with integrated electrical modulator-based sampling for headspace and online VOC analyses

“…With the FQImod as proxy for the coffee flavour, we demonstrate that with shortening of the GC runtime to 15 s the fastGC-SPI-TOFMS is capable to gather the rapid the flavour formation, occurring within 2 min, from roast gas analysis of a commercial drum roaster with a realistic roast profile. Most likely, also the on-line prediction of other coffee properties , such as roast degree or antioxidant capacity, which have been modelled from photoionisation TOFMS data 38,46 , would benefit from the enhanced chemical specificity of the fastGC addition.…”