2 research outputs found
Screening Method for the Visual Discrimination of Olive Oil from Other Vegetable Oils by a Multispecies DNA Sensor
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
Quantitative Bioluminometric Method for DNA-Based Species/Varietal Identification in Food Authenticity Assessment
A method is reported for species quantification by exploiting
single-nucleotide
polymorphisms (SNPs). These single-base changes in DNA are particularly
useful because they enable discrimination of closely related species
and/or varieties. As a model, quantitative authentication studies
were performed on coffee. These involved the determination of the
percentage of Arabica and Robusta species based on a SNP in the chloroplastic
trnL(UAA)-trnF(GAA) intraspacer region. Following polymerase chain
reaction (PCR), the Robusta-specific and Arabica-specific fragments
were subjected to 15 min extension reactions by DNA polymerase using
species-specific primers carrying oligo(dA) tags. Biotin was incorporated
into the extended strands. The products were captured in streptavidin-coated
microtiter wells and quantified by using oligo(dT)-conjugated photoprotein
aequorin. Aequorin was measured within 3 s via its characteristic
flash-type bioluminescent reaction that was triggered by the addition
of Ca<sup>2+</sup>. Because of the close resemblance between the two
DNA fragments, during PCR one species serves as an internal standard
for the other. The percentage of the total luminescence signal obtained
from a certain species was linearly related to the percent content
of the sample with respect to this species. The method is accurate
and reproducible. The microtiter well-based assay configuration allows
high sample throughput and facilitates greatly the automation