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Discrimination of Green Arabica and Robusta Coffee Beans by Raman Spectroscopy
Zitatschlüssel Keidel2010
Autor Keidel, Anke and von Stetten, David and Rodrigues, Carla and Maguas, Cristina and Hildebrandt, Peter
Seiten 11187-11192
Jahr 2010
ISSN 0021-8561
DOI 10.1021/jf101999c
Adresse 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Jahrgang 58
Nummer 21
Monat NOV 10
Zusammenfassung This paper presents an approach that may be applied as an accurate and rapid tool for classifying coffee beans on the basis of the specific kahweol content. Using Fourier-transform Raman spectroscopy with 1064 nm excitation it is possible to monitor the characteristic Raman bands of kahweol in green coffee beans without chemical and physical processing of the beans. The procedure was optimized on the basis of 83 and 125 measurements of whole and ground beans, respectively, using coffee samples of two different species, Coffee arabica L. and Coffee canephora L. (var. Robusta), and different origins (Asia, Africa, and South America). The relative contribution of the kahweol in individual beans can be determined quantitatively by means of a component analysis of the spectra, yielding a spectral kahweol index (sigma(ka)) that is proportional to the relative content of kahweol in a coffee bean. The reproducibility of the spectroscopic measurement and analysis was found to be 3.5\%. Individual beans of the same type and origin reveal a scattering of the sigma(ka) values. Nevertheless, an unambiguous distinction between Arabica and Robusta samples is possible on the basis of single-bean measurements as the sigma(ka) values are greater than and less than 10 for Arabica and Robusta coffees, respectively. Measurements of whole and ground beans afforded very similar results, despite the heterogeneous distribution of kahweol within a bean. Unlike conventional analytical techniques, the single-bean sensitivity of the present approach may also allow for a rapid detection of unwanted admixtures of low-value Robusta coffee to high-quality and more expensive Arabica coffee.
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