Single Origin Coffee Aroma: From Optimized Flavor Protocols and Coffee Customization to Instrumental Volatile Characterization and Chemometrics

Abstract

In this study, the aroma profile of 10 single origin Arabica coffees originating from eight different growing locations, from Central America to Indonesia, was analyzed using Headspace SPME-GC-MS as the analytical method. Their roasting was performed under temperature–time conditions, customized for each sample to reach specific sensory brew characteristics in an attempt to underline the customization of roast profiles and implementation of separate roastings followed by subsequent blending as a means to tailor cup quality. A total of 138 volatile compounds were identified in all coffee samples, mainly furan (~24–41%) and pyrazine (~25–39%) derivatives, many of which are recognized as coffee key odorants, while the main formation mechanism was the Maillard reaction. Volatile compounds’ composition data were also chemometrically processed using the HCA Heatmap, PCA and HCA aiming to explore if they meet the expected aroma quality attributes and if they can be an indicator of coffee origin. The desired brew characteristics of the samples were satisfactorily captured from the volatile compounds formed, contributing to the aroma potential of each sample. Furthermore, the volatile compounds presented a strong variation with the applied roasting conditions, meaning lighter roasted samples were efficiently differentiated from darker roasted samples, while roasting degree exceeded the geographical origin of the coffee. The coffee samples were distinguished into two groups, with the first two PCs accounting for 73.66% of the total variation, attributed mainly to the presence of higher quantities of furans and pyrazines, as well as to other chemical classes (e.g., dihydrofuranone and phenol derivatives), while HCA confirmed the above results rendering roasting conditions as the underlying criterion for differentiation.

Review on factors affecting coffee volatiles: from seed to cup

“…These studies considered that different roasting degrees (light, medium, dark) contributed to diverse classes of VOCs including, remarkably, the compounds 2-ethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, 4-vinylguaiacol, 2,3-pentanedione, 2-methylbutanal, 2-ethylguaiacol, 2,5-dimethylpyrazine and 2,3-dimethylpyrazine. 71,72 It has been indicated that light roasting, widely utilized in a cup test for sensory evaluation of green seed quality, produces volatile compounds such as furfural (sweet almond notes) and 2-methyl-butanol (buttery notes), which have a strong influence on aroma. With an increase in the degree of roasting (from light to medium), some compounds such as furans and volatile acids that are responsible for floral and fresh flavor become less crucial, probably resulting from losses as temperature increases, or from exposure to a higher temperature for a long time.…”

Characterization of the volatile organic compounds produced from green coffee in different years by gas chromatography ion mobility spectrometry

“…24 Meanwhile, the VOCs in green coffee were changed after roasting, which were also the reason for the difference. 6 The results of significance analysis showed that the contents of acids and esters in fresh green coffee (in 2020) changed significantly from 2019 to 2015, alcohols, aldehydes and alkenes changed significantly from 2018 to 2015, and ketones changed significantly from 2016 to 2015.…”

Volatile Compound Characterization of Coffee (Coffea arabica) Processed at Different Fermentation Times Using SPME–GC–MS

“…As observed in Figure 4 D, the content of 2-furanmethanol did not have significant changes between fermentation the processes and times, due to the mechanisms of reaction necessary for the synthesis of 2-furanmethanol, such as the Maillard reaction, and other thermal processes, such as oxide thermal degradation of polyunsaturated fatty acids, thiamine, nucleosides, sugars presented during caramelization, carbohydrates, ascorbic acid, and unsaturated fatty acids degradation, processes that require thermal intervention [ 44 ]. Moreover, 2-furanmethanol adds roasted aromas, and it is generated by the thermal process that degrades carbohydrates and sugars, such as hexoses and pentoses [ 45 ]; but the content of 2-furanmethanol cannot be high, because it generates an undesirable burnt and bitter smell [ 44 ].…”