Plastid trnH-psbA intergenic spacer serves as a PCR-based marker to detect common grain adulterants of coffee (Coffea arabica L.)

The present work describes the utilization of interspecific length polymorphisms within the chloroplastic trnH-psbA intergenic spacer to standardize a DNA-based method that identifies adulteration in Arabica coffee (Coffea arabica L.). Adulteration of coffee with roasted cereal grains and soybean is a common fraudulent practice, yet, research to design sensitive DNA-based tests in order to establish traceability in coffee is extremely limited. In the present study, PCR-CE (PCR-capillary electrophoresis) analysis of the trnH-psbA intergenic spacer proved successful to discriminate Arabica coffee and its common adulterants, namely corn, soybean, rice, wheat and barley. When the barcode PCR-CE assay was tested on admixtures, adulteration as low as 1% was successfully detected simply through barcode amplification and capillary electrophoresis separation. Moreover, it is important to note that the proposed barcode assay not only detects adulteration but also reveals the identity of the adulterant species based on barcode amplification profiles obtained from reference sets of anticipated adulterants.