Metabolomics fingerprint of Philippine coffee by SPME-GC-MS for geographical and varietal classification

Volatile metabolites of Philippine Arabica and Robusta coffee beans in the both forms standard (not-eaten by the Asian palm civet) and civet coffee grown in different Philippine regions were identified using the hyphenated technique headspace-solid phase microextraction-gas chromatography-mass spectrometry. A great number of volatile metabolites with a wide variety of functional groups were extracted and forty-seven prominent compounds were identified. The volatile metabolomics (volatilomics) fingerprint of Arabica coffees considerably differed with Robusta coffee and geographical origin slightly altered the fingerprint profile of coffee samples. Chemometric analysis such as principal component analysis (PCA) displayed a good classification between Arabica and Robusta coffee samples. Although, Arabica coffee samples from different geographical origins were clustered separately from each other, the proximity of clusters between Arabica coffee samples which can be classified into one large group, indicated their close similarity of headspace metabolites. PCA also identified several key volatile metabolites for the distinction of this group from Robusta coffees which is attributed to the higher amount of acetic acid, furfural, 5-methylfurfural, 2-formylpyrrole, and maltol, and lower concentration of 4-ethylguaiacol and phenol in all Arabica samples. These discriminating metabolites could be useful quality markers to differentiate Arabica with Robusta coffee. Results revealed that the headspace metabolites in coffee provide significant information on its inherent aroma quality. Also, the findings suggested that the overall quality of Philippine coffee is variety and region specific.