Olive oil is a prominent agricultural product which,
in addition
to its nutritional value and unique organoleptic characteristics,
offers a variety of health benefits protecting against cardiovascular
disease, cancer, and neurodegenerative diseases. The assessment of
olive oil authenticity is an extremely important and challenging process
aimed at protecting consumers and producers. The most frequent adulteration
involves blending with less expensive and readily available vegetable/seed
oils. The methods for adulteration detection, whether based on changes
in metabolite profiles or based on DNA markers, require advanced and
expensive instrumentation combined with powerful chemometric and statistical
tools. To this end, we present a simple, multiplex, and inexpensive
screening method based on the development of a multispecies DNA sensor
for sample interrogation with the naked eye. It is the first report
of a DNA sensor for olive oil adulteration detection with other plant
oils. The sensor meets the 2-fold challenge of adulteration detection,
i.e., determining whether the olive oil sample is adulterated and
identifying the added vegetable oil. We have identified unique, nucleotide
variations, which enable the discrimination of seven plant species
(olive, corn, sesame, soy, sunflower, almond, and hazelnut). Following
a single PCR step, a 20 min multiplex plant-discrimination reaction
is performed, and the products are applied directly to the sensing
device. The plant species are visualized as red spots using functionalized
gold nanoparticles as reporters. The spot position reveals the identity
of the plant species. As low as <5–10% of adulterant was
detected with particularly good reproducibility and specificity.