Characterisation of stored Arabica and Robusta coffees by headspace-GC and sensory analyses

Abstract

The changes in roasted ground Arabica and Robusta coffees were studied during 18 months' storage by headspace gas chromatography and by sensory analyses. Arabica coffee contained more dimethyl sulphide, 2-methylpropanal, butanedione, 2,3-pentanedione, 2-furaldehyde, and 3-methylbutanal than Robusta. Robusta contained more phenol, toluene, 1-methylpyrrole, thiophene, 2-hydroxyphenol, 2,5-dimethylpyrazine, and furfuryl acetate than Arabica, although the amounts of the compounds were quite small. The clearest sensory differences observed between Arabica and Robusta coffee brews were in cocoa, papery, and brown sugar odours at every storage time evaluated. Robusta coffee had less cocoa and brown sugar, but more earthy, papery, and burnt odour characteristics than Arabica. Useful indicators of ageing were the ratios 2-methylfuran/2-butanone, acetone/propanal, and 2-methylfuran/propanal. Storage of the coffee at room temperature for 18 months did not significantly alter the perceived intensities of the odour characteristics.