Isotopic and Elemental Composition of Roasted Coffee as a Guide to Authenticity and Origin

Abstract

This study presents the stable isotopic and elemental compositions of single-origin, roasted coffees available to retail consumers. The δ(13)C, δ(15)N, and δ(18)O compositions were in agreement with those previously reported for green coffee beans. The δ(15)N composition was seen to be related to organic cultivation, reflected in both δ(2)H and δ(18)O compositions. The δ(13)C composition of extracted caffeine differed little from that of the bulk coffee. Stepwise discriminant analysis with jackknife tests, using isotopic and elemental data, provided up to 77% correct classification of regions of production. Samples from Africa and India were readily classified. The wide range in both isotopic and elemental compositions of samples from other regions, specifically Central/South America, resulted in poor discrimination between or within these regions. Simpler X-Y and geo-spatial plots of the isotopic data provided effective visual means to distinguish between coffees from different regions.