Characterization of Headspace Aroma Compounds of Freshly Brewed Arabica Coffees and Studies on a Characteristic Aroma Compound of Ethiopian Coffee

Abstract

A sampling method to isolate headspace volatiles of freshly brewed drip coffee using a solid-phase microextraction fiber (fiber type: divinylbenzene/carboxen/polydimethylsiloxane) in a short time (2 min) immediately after extraction has been developed. Volatile compounds and potent odorants obtained from each headspace aroma of various arabica coffee extracts (3 production countries: Ethiopia, Tanzania, and Guatemala; 3 roasting degrees for each country: L26, L23, and L18) using the sampling method were examined by gas chromatography/mass spectrometry (GC/MS) and GC/olfactometry (GC/O, CharmAnalysis). The results of principal component analysis (PCA) using the data of GC/O analysis showed that the aroma profile of Ethiopian coffee was discriminately different from those of Tanzanian coffee and Guatemalan coffee. In addition, it was suggested from the factor loading of the PCA that 4-(4'-hydroxyphenyl)-2-butanone (raspberry ketone; sweet-fruity odor) characterized the aroma profile of freshly brewed Ethiopian coffee. Therefore, the 4-(4'-hydroxyphenyl)-2-butanone was quantified in the 9 kinds of coffee extracts. Ethiopian coffee extract of the lightly roasted degree (roasting degree: L26) contained the highest amount of this component, while it was only a little over the reported threshold. In the sensory test, the headspace aromas of Tanzanian and Guatemalan coffees in which 4-(4'-hydroxyphenyl)-2-butanone was added were, respectively, discriminated from not added samples, and "sweet" odor was selected as an odor description that assessors found similarity between the added Tanzanian or Guatemalan coffee aroma and the Ethiopian coffee aroma. It was suggested that 4-(4'-hydroxyphenyl)-2-butanone made some detectable change on total aroma profile even though the added amount was only near threshold level.

Evolution of sensory aroma attributes from coffee beans to brewed coffee

“…Czerny et al (1999) found that attributes such as roasted, earthy, and smoky increased with degree of roasting. Akiyama et al (2008) reported smoke/roast, phenolic, sweet/caramel, and green to be positively correlated with degree of roasting, while sweet/fruity and acidic attributes to be negatively correlated. Sarrazin et al (2000) reported 'roasted biscuit', 'peanut', 'caramel', 'toasted bread', and 'cereal' to be the sensory notes for light roasted coffee.…”

The compositional basis of coffee flavour

“…Some of the compounds being investigated, particularly the volatile terpenes, have not previously been quantified accurately although their presence and peak abundance have been reported previously (Del Terra et al, 2013, Gonzalez-Rios et al, 2007, Mondello et al, 2005, Akiyama et al, 2008. Mostly found in coffee flowers and berries, terpenes are known to remain in the roasted coffee beans and corresponding brews (Stashenko et al, 2013, Emura et al, 1997, Akiyama et al, 2008. As known contributors the boquet of wines and beers, these monoterpenes are also likely to influence coffee flavour.…”

“…The separation is based on partitioning or distribution of a sample between a moving (mobile) phase (gas), and a fixed or stationary phase (Wittkowski and Matissek, 1993). In combination with a GC, chemical detection of coffee flavour compounds can be conducted such as via a flame ionisation detector (FID) (Ribeiro et al, 2010, Ribeiro et al, 2012 or mass selective detector (MSD) (Akiyama et al, 2007, Akiyama et al, 2008. However, coupling a GC to a Mass Spectrometer (MS) has been reported to provide several advantages in flavour research due to its high sensitivity detection and the faster scan rates required for the GC peaks identification and traces analysis (McNair and Miller, 1998).…”

“…The studies that have correlated physicochemical and olfactory or sensory panel data typically analysed a limited range of coffee flavour-types (Akiyama et al, 2008, Bhumiratana et al, 2011, Pérez-Martínez et al, 2008, Ribeiro et al, 2012, Ribeiro et al, 2009, Kerler et al, 2014, Charles et al, 2015. Certainly there is scope for future research efforts to model coffee flavour more comprehensively in terms of the range of sensory properties exhibited in Arabica coffees from around the world.…”

“…Compounds identified as important contributors, concentration measured and/or aroma description and aroma threshold provided in literatures 1 ; 2 ; 3 (Akiyama et al, 2003);1992); 12 (Akiyama et al, 2007); 13 (Ribeiro et al, 2012); 14 ; 15 (Cheong et al, 2013); 16 ; 17 ; 18 (Kumazawa and Masuda, 2003); 19 (Blank et al, 1991); 20 (Akiyama et al, 2008); 21 (Czerny et al, 1996); 22 (Balzer, 2001); 23 (Grosch, 2001b); 24 (Gianturco et al, 1964); 25 (Silwar et al, 1987); 26 (Milo and Grosch); 27 (Belitz et al, 2009); 28 (Burdock, 2010); 29 (Czerny et al, 2008); 30 (Salo, 1970); 31 (Barrett et al, 1983); 32 (Larsen and Poll, 1992); 33 (Buttery and Ling, 1997).…”