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

This study presents the stable isotopic
and elemental compositions
of single-origin, roasted coffees available to retail consumers. The
δ13C, δ15N, and δ18O compositions were in agreement with those previously reported for
green coffee beans. The δ15N composition was seen
to be related to organic cultivation, reflected in both δ2H and δ18O compositions. The δ13C 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.