Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 3.15

Microsatellite analysis of green and roasted coffee blends for authenticity and traceability

MARTELLOSSI C.*^,**, BATES J.E.**, TAYLOR E.J.**, DE NARDI B.*, GRAZIOSI G.*

*) Università degli Studi di Trieste

**) NIAB, Cambridge, UK

coffee, SSR, DNA traceability

World coffee production relies on just two species, Coffea arabica and C. canephora. The former accounts for 70% of the market and is associated with a better quality product: the latter is usually employed in blends, e.g. for espresso or instant coffee. The use of molecular markers to identify species or varieties within a blend is a way for the importers/roasters to guarantee a product of constant quality and prevent adulteration from extraneous species or lower grade varieties.

In order to assess the traceability of molecular markers in the commercial products, we have developed several methods for the extraction of PCR-grade DNA from green and roasted beans and instant coffee and its subsequent amplification.

These techniques allowed us to screen 25 different blends of green coffee (bulks of 20 seeds in each sample) for DNA polymorphisms using 46 microsatellite primer pairs. The data from this microsatellite analysis was used to select samples for further studies. These included VNTR analysis of DNA extracted from 5 individual seeds for each sample to observe the degree of variabilty within a blend.

To evaluate the traceability of molecular markers during the various steps of the production process, we used microsatellite primers that would amplify products of an expected size that was no larger than 150bp. This was to increase the probability of successful amplification even with partial degradation of DNA, which will occur during the roasting process. DNA extracted from samples of commercial coffee taken out at different stages of the roasting process was used for this latter analysis.

The results obtained support the data provided by other research that has demonstrated the scarcity of DNA polymorphisms in C. arabica. This is largely due to the peculiar history of this crop, in which self-pollination and bottleneck effects combined in keeping intra-specific variability to a very low level.