Authentication of the Origin, Variety and Roasting Degree of Coffee Samples by Non-Targeted HPLC-UV Fingerprinting and Chemometrics. Application to the Detection and Quantitation of Adulterated Coffee Samples

Abstract

In this work, non-targeted approaches relying on HPLC-UV chromatographic fingerprints were evaluated to address coffee characterization, classification, and authentication by chemometrics. In general, high-performance liquid chromatography with ultraviolet detection (HPLC-UV) fingerprints were good chemical descriptors for the classification of coffee samples by partial least squares regression-discriminant analysis (PLS-DA) according to their country of origin, even for nearby countries such as Vietnam and Cambodia. Good classification was also observed according to the coffee variety (Arabica vs. Robusta) and the coffee roasting degree. Sample classification rates higher than 89.3% and 91.7% were obtained in all the evaluated cases for the PLS-DA calibrations and predictions, respectively. Besides, the coffee adulteration studies carried out by partial least squares regression (PLSR), and based on coffees adulterated with other production regions or variety, demonstrated the good capability of the proposed methodology for the detection and quantitation of the adulterant levels down to 15%. Calibration, cross-validation, and prediction errors below 2.9%, 6.5%, and 8.9%, respectively, were obtained for most of the evaluated cases.

High‐performance liquid chromatography with fluorescence detection fingerprints as chemical descriptors to authenticate the origin, variety and roasting degree of coffee by multivariate chemometric methods

“…The obtained HPLC‐FLD fingerprints also appear to be richer compared to HPLC‐UV fingerprints regarding the number of extracted compounds that can be detected 13 . Moreover, these fingerprints are also very reproducible within the coffee samples of the same type.…”

“…For example, the depicted coffee samples from Colombia and Ethiopia (Fig. 1a,b), both of the Arabica variety, displayed much higher intensities compared to the other samples as a result of the presence of a high intensity signal at a retention time of approximately 17 min, which is attributed to the presence of caffeic acid 13 . Regarding the second set of samples (see Supporting information, Fig.…”

“…Authentication of the origin (country of production), variety and roasting degree of commercially available coffee samples is gaining relevance. In a previous study, 13 a non‐targeted HPLC‐UV fingerprinting method was developed for the characterization and authentication of coffee samples. It was concluded that HPLC‐UV fingerprints were good chemical descriptors for classifying certain groups of coffee samples, although they could not classify all the analyzed coffees (classification rates higher than 89.3% in some evaluated pairs of samples).…”

“…described the use of an electronic nose for the detection of volatile compound profiles in Arabica coffee from different regions of origin. In terms of separation techniques to identify and quantify coffee compounds, liquid chromatography (LC) coupled with UV 12,13 and fluorescence detection (FLD) 14,15 has been used. Other separation techniques usually employed are capillary electrophoresis (CE) 16,17 and gas chromatography (GC), 18 both coupled to mass spectrometry (MS).…”

“…In a previous work, a high‐performance liquid chromatography with UV detection (HPLC‐UV) fingerprinting method was proposed for the characterization and classification of coffee according to different quality attributes such as the region of origin, the variety (Arabica/Robusta) and the roasting degree 13 . Chromatographic separation was addressed by using C18 reversed‐phase column under gradient conditions employing 0.1% formic acid aqueous solution and methanol as the mobile phase with a total analysis time of 40 min.…”