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

The δ 13C, δ 15N and δ 18O compositions were in agreement with those previously reported for green coffee beans. The δ 15N composition was seen to be related to organic cultivation, reflected in both δ 2H and δ 18O compositions. The δ 13C composition of extracted caffeine differed little from that of the bulk coffee. Step-wise 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.

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