Fully Automated Identification of Coffee Species and Simultaneous Quantification of Furfuryl Alcohol Using NMR Spectroscopy

Abstract

Background Coffee is a popular beverage with two species, Coffea canephora and C. arabica, being commercially exploited. The quality and commercial value of coffee is dependent on species and processing. C. arabica typically obtains a higher price on the market compared to C. canephora. Coffee beans undergo roasting during processing, resulting in the formation of flavor compounds including furfuryl alcohol which has been classified by the International Agency for Research on Cancer as possibly carcinogenic to humans (Group 2B). Objective The aim of this study was to identify coffee species and other properties using nuclear magnetic resonance (NMR) spectroscopy, specifically to conduct quantification of the roasting process contaminant furfuryl alcohol. Method The quantification of furfuryl alcohol was performed from the NMR spectra using the pulse length-based concentration (PULCON) methodology. Prior to NMR analysis, samples were extracted using deuterated chloroform. Results Roasting experiments identified the maximum roasting temperature to be the most significant factor in the formation of furfuryl alcohol. Among the coffee species, C. canephora was found to contain a relatively lower amount of furfuryl alcohol compared to C. arabica. The roasting of wet processed coffee resulted in higher contents of furfuryl alcohol. Geographical origin and variety within species had no influence on the furfuryl alcohol content. Conclusion Validation results show that NMR spectroscopy is fit-for-purpose to obtain targeted information of coffee samples. Highlights The PULCON NMR methodology allows a simple, rapid and accurate determination of constituents of coffee.

Validation of a Quantitative Proton Nuclear Magnetic Resonance Spectroscopic Screening Method for Coffee Quality and Authenticity (NMR Coffee Screener)

“…All spectra were recorded with the basopt mode. The acquisition parameters were constant for all spectra for PULCON measurement according to Lachenmeier et al [26]. The FID was multiplied with exponential window function, and spectra were automatically phased, baseline-corrected using TopSpin version 3.2 and 3.5 (Bruker Biospin, Rheinstetten, Germany).…”

“…The peak areas were determined using a line fitting algorithm. Quantification was done using the eretic factor, which was previously determined using a quant reference (for details see [26]). At the end of each measurement series, a control solution was measured as a safeguard.…”

“…Nuclear magnetic resonance spectroscopy in combination with chemometrics has been applied either for routine quality control and/or detection of potentially harmful substances in beverages such alcohol [20], fruit juices [21,22] and coffee [8,23]. NMR spectroscopy may be applied for the quantification of caffeine, OMC, kahweol, 5-hydroxymethylfurfural (HMF) and furfuryl alcohol in coffee [24][25][26]. For decaffeinated coffee, NMR spectroscopy may be used to determine the residual quantities of caffeine, which would typically be less than 1 g/kg.…”

Validation of a Quantitative Proton Nuclear Magnetic Resonance Spectroscopic Screening Method for Coffee Quality and Authenticity (NMR Coffee Screener)

“…Nuclear magnetic resonance spectroscopy in combination with chemometrics has been applied either for routine quality control and/or detection of potentially harmful substances in beverages such as alcohol [20], fruit juices [21,22] and coffee [8,23]. NMR spectroscopy may be applied for the quantification of caffeine, OMC, kahweol, 5-hydroxymethylfurfural (HMF) and furfuryl alcohol in coffee [24][25][26]. For decaffeinated coffee, NMR spectroscopy may be used to determine the residual quantities of caffeine, which would typically be less than 1 g/kg.…”

Impact of B-Ring Substitution and Acylation with Hydroxy Cinnamic Acids on the Inhibition of Porcine α-Amylase by Anthocyanin-3-Glycosides

“…NMR spectra were analyzed using TopSpin version 3.5 pl. 6 (Bruker Biospin, Ettlingen, Germany) and compound concentrations were determined using the pulse length-based concentration determination (PULCON) principle according to [20][21][22]. A 1 H-NMR spectrum of a quantification reference solution (QuantRef), containing lactic acid and citric acid, was used to calculate the Electronic-Reference-to-access-in-vivo-Concentrations-(ERETIC) factor according to Equation (1).…”