Laser diode can combat counterfeit olive oil

Researchers in Spain and the US have designed a sensor that can detect counterfeit olive oil labelled as extra virgin or protected designation of origin (PDO).

The tool can distinguish between apparently similar oils that present notable differences in quality, according to the scientists from the Complutense University of Madrid (UCM) and the Scintillon Institute, who have published the work in the journal Talanta.

This is possible thanks to the use of laser diodes, because the fluorescence emitted by adulterated oils is slightly different to that of pure extra virgin olive oils. The tool is inexpensive both to use and to manufacture – in fact it can be made using a 3D printer, says the team.

“Other clear advantages of our tool include the possibility of conducting on-site analyses, because the equipment is the size of a briefcase and therefore portable, and of generating results in real time,” says José Torrecilla, a senior lecturer and researcher in the department of chemical engineering and materials at UCM.

“The quality of olive oil is recognised nationally and internationally. It is therefore necessary to protect this quality and combat the fraudulent activities carried out with increasing frequency and skill in the sector.”

Counterfeiting and fraud is a big problem for the $16bn-a-year olive oil industry, with some studies claiming that between 60 and 90 per cent of olive oils sold in the US are adulterated with cheaper pomace oil or oils from other plant species such as sunflower, canola and peanut.

Over three million tons annually of olive oil are produced worldwide, with around 75 per cent of this being produced in Italy, Spain and Greece.

To conduct the study, researchers mixed single-varietal, protected designation of origin oils with other protected designation of origin oils that were past their "best before" date. All the oils were purchased from shopping centre stores.

Subsequently, mixtures were made using oils with between 1 and 17 per cent acidity that were also past their ‘best before’ date. Lastly, measurements were performed using the sensor, which was manufactured with a 3D printer, and an analysis was conducted of the results obtained by means of chaotic algorithms.

In all cases, it was possible to determine the concentration of the adulterant in the binary sample, according to the scientists, who carried out a proof-of-concept using three PDO extra virgin olive oils (EVOOs) and three expired PDO EVOOs used as artificial adulterants.

“This technique is available for use at any time, and only requires oils prior to packaging for quality control or after packaging to detect fraudulent brands and/or producers,” says Torrecilla.

Image credit: ESENCIA ANDALUSÍ