Abstract
IntroductionIn the last years, consumers increased the demand for high-quality and healthy beverages, including coffee. To date, among the techniques potentially available to determine the overall quality of coffee beverages, metabolomics is emerging as a valuable tool.ObjectiveIn this study, 47 ground coffee samples were selected during the 2018 Edition of the “International coffee tasting” (ICT) in order to provide discrimination based on both chemical and sensory profiles. In particular, 20 samples received a gold medal (“high quality” group), while lower sensory scores characterized 27 samples (without medal).MethodsUntargeted metabolomics based on ultra-high pressure liquid chromatography coupled with quadrupole-time-of-flight (UHPLC-QTOF) and head space-gas chromatography coupled with mass spectrometry platforms followed by multivariate statistical approaches (i.e., both supervised and unsupervised) were used to provide new insight into the searching of potential markers of sensory quality.ResultsSeveral compounds were identified, including polyphenols, alkaloids, diazines, and Maillard reaction products. Also, the headspace/GC-MS highlighted the most important volatile compounds. Polyphenols were scarcely correlated to the sensory parameters, whilst the OPLS-DA models built using typical coffee metabolites and volatile/Maillard compounds possessed prediction values > 0.7. The “high quality” group showed specific metabolomic signatures, thus corroborating the results from the sensory analysis. Overall, methyl pentanoate (ROC value = 0.78), 2-furfurylthiol (ROC value = 0.75), and L-Homoserine (ROC value = 0.74) established the higher number of significant (p < 0.05) correlations with the sensory parameters.ConclusionAlthough ad-hoc studies are advisable to further confirm the proposed markers, this study demonstrates the suitability of untargeted metabolomics for evaluating coffee quality and the potential correlations with the sensory attributes.Graphic abstract
Highlights
In the last years, consumers increased the demand for high-quality and healthy beverages, including coffee
We aimed to evaluate the potential of metabolomics to discriminate ground coffees with different sensory quality, as reported by a panel of coffee tasters
The potential of untargeted UHPLC-QTOF mass spectrometry was tested, providing discrimination of 47 ground coffee samples collected during the “International Coffee Tasting” (ICT) competition (2018 Edition)
Summary
Consumers increased the demand for high-quality and healthy beverages, including coffee. Among the techniques potentially available to determine the overall quality of coffee beverages, metabolomics is emerging as a valuable tool. Results Several compounds were identified, including polyphenols, alkaloids, diazines, and Maillard reaction products. Polyphenols were scarcely correlated to the sensory parameters, whilst the OPLS-DA models built using typical coffee metabolites and volatile/Maillard compounds possessed prediction values > 0.7. The sensorial quality of coffee beverage can be affected by several factors, including harvesting and post-harvest, together with roasting and storage conditions. These latter are responsible for the production/degradation of several compounds, including carbohydrates, lipids, and other compounds (Kitzberger et al 2013, 2014; Cheng et al 2016; da Rosa et al 2016). During the roasting process, lipids are prone to decomposition and auto-oxidation reactions, contributing to both aroma and body of the beverage (Koskei et al 2015)
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