Discrimination between Arabica and Robusta Coffee Species on the Basis of Their Amino Acid Enantiomers

Abstract

This work reports the results for the composition of robusta and arabica coffee species in terms of their amino acid enantiomers in the green and roasted states. The analyses were conducted for the free amino acids, as well as for the amino acids obtained after acid hydrolysis. The amino acids were extracted/hydrolyzed and isolated by SPE on strong cation exchange columns, derivatized to their N-ethoxycarbonylheptafluorobutyl esters, and analyzed by gas chromatography/FID on a Chirasil l-Val column. Multivariate analyses applied to the results showed that the free amino acids can be used as a tool for discrimination between coffee species, with a special reference to l-glutamic acid, l-tryptophan, and pipecolic acid. There is also some evidence that these compounds can be used for discrimination between green coffees subjected to different postharvest processes. It is also shown that the amino acid levels observed after acid hydrolysis can be used for the same purposes, although displaying less discriminatory power.