Comparative evaluation of flavor compounds in fermented green and roasted coffee beans by solid phase microextraction‐gas chromatography/mass spectrometry

Abstract

Specific fermentation processes such as digestive bioprocessing and monsooning have been of interest to coffee consumers. Volatile compounds of beans during the different fermentation processes vary considerably and exhibit different profiles. The representative flavor compounds for the luwak green bean were found to be pentamethyl heptane and 3‐methyl‐1‐butanol, while more diverse and distinct compounds were observed from the monsooned green bean, namely alkyl butanals, pinenes, benzaldehyde and butanediols. However, after roasting, the fermented form of both beans contained similar types of volatiles and their relative contents compared to those of non‐fermented roasted beans, except for α‐pinene in luwak and 2‐methyl furan in monsooned beans. In principal components analysis and partial least squares‐discriminant analysis (PLS‐DA), the different fermented beans were clearly distinguished by the extracted peak entities from their total ion chromatograms. The s‐plot and variable importance on projection (VIP) values related to PLS‐DA showed the significant compounds contributing to the identification of the groups. 3‐Methyl‐1‐butanol was the most distinctive compound for the luwak green bean, and β‐pinene, ethylbenzene and benzaldehyde were found to be the significant compounds in the monsooned green bean. In roasted beans, the most significant compounds to distinguish luwak were furfural, α‐pinene and 3‐carene with high variable in the projection (VIP) values. A significant presence of pyrazine, alkyl pyrazines, pyridine and alkyl pyridines contributed to differentiating both fermented roasted coffee beans from the unfermented roasted beans.

Changes in volatile compounds of fermented minced pepper during natural and inoculated fermentation process based on headspace–gas chromatography–ion mobility spectrometry

“…It indicated that some furans were generated during fermentation process. Furans were hardly detected in many fermented foods(Kim et al, 2019). It is indicated that 2-ethylfuran, 2-pentyfuran, and 2-acetylfuran were probably the characteristic volatile compounds in FMP.…”

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

“…The results in Figure 4 B show that the content of 2-methylpyrazine in the dry anaerobic and the atmosphere modified with CO 2 processes decreased, but it was stable after 24 h. The reason why 2-methylpyrazine, as some pyrazines, did not increase during the fermentation process was because these microorganisms did not have a significant impact in terms of content during the fermentation process [ 40 ]. Most pyrazines are synthetized from a Maillard reaction, a process that requires a thermal reaction [ 12 ]. However, in the dry aerobic fermentation, there was an increase in 2-methylpyrazine until 48 h of fermentation, because the aerobic fermentation of coffee contains a heterogeneous microorganism population [ 41 ], while the anaerobic fermentation process contains a homogeneous population [ 24 ].…”

“…2,6-Dimethylpyrazine brings a sweet nutty–fruity aroma [ 11 ]. The results in Figure 4 E determined that during the fermentation time, the content of 2,6-dimethylpyrazine decreased, because this compound has a tendency to decrease during a fermentation process [ 12 ]. At controlled times of fermentation, the content of 2,6-dimethylpyrazine decreased, while acid compounds increased [ 10 ], because the interaction between carbohydrates and α-amino acids are necessary for the synthesis of 2,6-dimethylpyrazine [ 46 ]; so, as the fermentation time increased, complex carbohydrates were degraded to simple carbohydrates [ 47 ], reducing the content of the substrate necessary for 2,6-dimethylpyrazine synthesis.…”

“…For the extraction of these compounds, several techniques have been applied in the food industry for quality control. Nevertheless, solid phase microextraction (SPME) is a simple extraction method, solventless, robust, and replicable, because the fiber accumulates analytes with different types of sorbents, improving coffee volatile compound extraction [ 12 ].…”

Untargeted HILIC-MS-Based Metabolomics Approach to Evaluate Coffee Roasting Process: Contributing to an Integrated Metabolomics Multiplatform

“…These markers decreased during roasting process. All the identified compounds grouped in Tables 2 and 3 had been previously described in coffee samples in the literature [25,26,[30][31][32][33].…”