Enhancing the Understanding of Aroma Formation during Coffee Roasting Using DHS-GC×GC-TOFMS and Chemometrics

This study integrates advanced chromatographic techniques and chemometric analysis to deepen the understanding of volatile and semivolatile compound formation during coffee roasting. Dynamic headspace extraction (DHS) was used to capture these compounds at three distinct roasting stages. The volatiles were analyzed and identified using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS), a high-resolving power technique to reliably annotate the numerous features present in the aroma-profile. Partial least-squares discriminant analysis (PLS-DA) was used to handle the large and complex data generated by GC×GC-TOFMS. This method successfully classified samples based on the roasting stages. Evaluation of the loadings using a variable importance in projection (VIP) approach revealed that 99 aroma-related volatiles varied significantly during coffee roasting, including carboxylic acids (e.g., acetic acid) and pyrazines such as 2-ethenyl-5-methyl pyrazine and ethyl pyrazine. These compounds exhibited distinct kinetic profiles, providing a detailed understanding of the chemical transformations occurring during roasting. This research describes an important methodology for monitoring aroma-related volatiles that may be useful for personalized coffee roasting, delivering key insights into the complex development of coffee aroma.