Dipstick test for DNA-based food authentication. Application to coffee authenticity assessment.
This paper reports DNA-based food authenticity assays, in which species identification is accomplished by the naked eye without the need of specialized instruments. Strongly colored nanoparticles (gold nanoparticles) are employed as reporters that enable visual detection. Furthermore, detection is performed in a low-cost, disposable, dipstick-type device that incorporates the required reagents in dry form, thereby avoiding multiple pipetting and incubation steps. Due to its simplicity, the method does not require highly qualified personnel. The procedure comprises the following steps: (i) PCR amplification of the DNA segment that flanks the unique SNP (species marker); (ii) a 15 min extension reaction in which DNA polymerase extends an allele-specific primer only if it is perfectly complementary with the target sequence; (iii) detection of the products of the extension reaction within a few minutes by the naked eye employing the dipstick. No purification is required prior to application of the extension products to the dipstick. The method is general and requires only a unique DNA sequence for species discrimination. The only instrument needed is a conventional thermocycler for PCR, which is common equipment in every DNA laboratory. As a model, the method was applied to the discrimination of  Coffea robusta  and  arabica  species in coffee authenticity assessment. As low as 5% of Robusta coffee can be detected in the presence of Arabica coffee.
Department of Chemistry, University of Patras, Patras, Greece 26504.
Ioannis A
IA
Trantakis
Stelios
S
Spaniolas
Panagiotis
P
Kalaitzis
Penelope C
PC
Ioannou
Gregory A
GA
Tucker
Theodore K
TK
Christopoulos
D040503:Coffea / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics*; D005504:Food Analysis / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D005838:Genotype; D016133:Polymerase Chain Reaction / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D020641:Polymorphism, Single Nucleotide
D018744:DNA, Plant