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

Abstract

Monitoring coffee quality as a means of detecting and preventing economically motivated fraud is an important aspect of international commerce today. Therefore, there is a compelling need for rapid high throughput validated analytical techniques such as quantitative proton NMR spectroscopy for screening and authenticity testing. For this reason, we sought to validate an NMR spectroscopic method for routine screening of coffee for quality and authenticity. A factorial experimental design was used to investigate the influence of NMR device, extraction time and nature of coffee on the content of caffeine, 16-O-methylcafestol (OMC), kahweol, furfuryl alcohol and 5-hydroxymethylfurfural (HMF) in coffee. The method was successfully validated for specificity, selectivity, sensitivity and linearity of detector response. The proposed method produced satisfactory precision for all analytes in roasted coffee, except for kahweol in canephora (robusta) coffee. The proposed validated method may be used for routine screening of roasted coffee for quality and authenticity control, as its applicability was demonstrated during the recent OPSON VIII Europol-Interpol operation on coffee fraud control.

16‐O‐Methylated diterpenes in green Coffea arabica: ultra‐high‐performance liquid chromatography‐tandem mass spectrometry method optimization and validation

“…Arabica green coffee samples from different geographical origins representative of the most important Arabica production areas were subjected to the 16‐OMD quantitative characterization (in Figure S2A and in Figure S2B, the UHPLC‐MS chromatograms of 16OMC in Brazil, Colombia, Guatemala and Ethiopia2 samples). 16‐ O ‐Methylated diterpene content shown in Table 3 is remarkably below the expected Arabica guidance value of <50 mg/kg recently reported 27 . In all of the analyzed samples, the content of 16‐OMD is even lower than 20 mg/kg, in full agreement with reported data on several Arabica cultivars albeit roasted 14 .…”

“…In the case of Arabica, the total 16‐OMD content determined by NMR in several samples of roasted Arabica cultivars was found to be <20 mg/kg, 14 and very recently for this coffee species, a guidance value of 16‐OMC content <50 mg/kg was used for authentication purposes 27 . As far as the relative proportion of the two 16‐OMD is concerned, the obtained data indicate that 16‐OMC accounts for approximately 90% of the total 16‐OMD present in the analyzed green Arabusta coffee.…”

“…After full validation, the method was successfully applied to the analysis of several real Arabica samples. It should be stressed that the 16‐OMD trace amounts found in most of the real Arabica samples are below the reported LOQ determined by NMR methods and ranging from 7.4 to 20 mg/kg 7,27 . This aspect should be carefully taken into consideration to select the most appropriate analytical method to detect and quantify the 16‐ O ‐methylated diterpenes in green Arabica coffee.…”

Cold Brew Coffee—Pilot Studies on Definition, Extraction, Consumer Preference, Chemical Characterization and Microbiological Hazards

“…The following parameters were defined: spectral width 20.55 ppm (8223.69 Hz), number of scans 32, dummy scans 4, acquisition time from 3.98 s, receiver gain of 16, dwell time from 60.80, delay (d1) of 4 s and a delay (d7) of 5 s. For an optimal pulse length, a calibration was performed for each measurement. The quantitative analysis took place via TopSpin software (Bruker, Rheinstetten, Germany) and using a MATLAB (Mathworks, Natick, MA, USA) script for automated integration (for details, see [ 9 , 10 , 11 ]). Graphs were generated using Prism 6 (GraphPad Software, San Diego, CA, USA).…”