Screening and distinction of coffee brews based on headspace solid phase microextraction/gas chromatography/principal component analysis

Abstract

The volatile profiles of espresso and plunger (cafetière) coffees prepared from (1) an 80:20 (w/w) blend of natural roasted Robusta and Arabica (Robusta Natural blend), (2) a 40:40:20 (w/w/w) blend of Robusta Natural blend, Robusta torrefacto roast (850 g kg −1 Robusta, 150 g kg −1 sugar) and (3) natural roasted pure Arabica were established by headspace solid phase microextraction (SPME) after selection of the fibre coating (polyacrylate or polydimethylsiloxane) and the temperature and time of extraction. For the analysis of furans and indoles the polyacrylate coating proved to be more suitable; however, for the overall characterisation of the volatile composition of espresso and plunger coffees the polydimethylsiloxane coating was chosen. SPME/gas chromatography (GC)/mass spectrometry (MS) analyses allowed the identification of 37 compounds: four aldehydes, two ketones, 11 furans, 10 pyrazines, two pyridines, three phenolic compounds, two indoles, one lactone, one ester and one benzothiazine. The volatile composition was related more to the botanical variety (Arabica or Robusta) than to the method of preparation of the brew (espresso or plunger). Furthermore, use of the variability provided solely by the GC peak areas and respective retention times, combined with principal component analysis (PCA), yielded the information necessary for discrimination. The combined technique of headspace SPME/GC/PCA, as an alternative to conventional techniques based on GC/MS, is proposed as a lower-cost, fast and reliable technique for the screening and distinction of coffee brews.

Chromatographic Methods for Coffee Analysis: A Review

“…Identifying characteristics of coffee at different stages of its production are determined by: the shape and size of coffee beans, its organoleptic characteristics, element compositions (Krivan et al, 1993;Weckerle et al, 2002;Serra et al, 2001;Wieser et al, 2002;Rodrigues et al, 2010), aroma analysis , physical and chemical composition (Rocha et al, 2004;Ky et al, 2001;Casals et al, 2000;Guerrero et al, 2001;Carrera et al, 1998;Valdenbro et al, 1999 ;Bertrand et al, 2005;Martin, et al, 2001;Gonzales et al, 2001;Anderson et al, 2002;Kemsley et al, 1995;Dupuy et al, 1995;Suchanek et al, 1996;Downey et al, 1996). For identification of botanical species of coffee beans, assessment of the outward anatomy and morphology may sufficient.…”

Using hyperspectral imaging to characterize consistency of coffee brands and their respective roasting classes

“…The organic compounds that result from roasting of coffee beans have been studied for over 50 years (Rhoades, 1960), and more than 850 substances have been identified from volatile fractions of roasted coffee (Franca et al, 2009;Rocha et al, 2004;Yeretzian et al, 2014). The chemical changes during the roasting process are associated with Maillard and Strecker reactions, amino acid and protein degradations, and changes to profiles of polysaccharides and trigonelline and chlorogenic acids (De Maria et al, 1996;Duarte et al, 2005;Montavon et al, 2003;van Boekel, 2006).…”

Comparison of two extraction methods for evaluation of volatile constituents patterns in commercial whiskeysElucidation of the main odour-active compounds

“…Moreover, it is fast, inexpensive and requires small sample volumes. This technique, based on absorption and/or adsorption mechanism, depending on the fibre coating, can be successfully applied for polar and non-polar compounds in gaseous, liquid and solid samples and can be easily coupled with various analytical instruments such as GC, GC-MS, HPLC and LC-MS [16][17][18][19][20][21][22][23]. It has been used routinely in combination with gas chromatography (GC) and gas chromatography coupled to mass spectrometry with ion trap detection (GC-ITD MS), and successfully applied to a wide variety of compounds, especially for the extraction of volatile and semi-volatile organic compounds from environmental [24], biological [25] and food [26][27][28][29][30][31] samples.…”