Laser diode system detects counterfeit olive oils

02 Jan 2019

Researchers at UCM Madrid and Scintillon Institute (US) develop sensor to detect fake oil – such as ordinary types sold as "extra virgin".

Researchers at the Complutense University of Madrid, Spain, (UCM) and the Scintillon Institute in San Diego, Ca, US, have designed an optical sensor that can detect counterfeit olive oil labeled as extra virgin or protected designation of origin.

The tool, reported in the Elsevier jornal Talanta, can distinguish between apparently similar oils that present notable differences in quality. 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.

Extra virgin olive oil is made from pure, cold-pressed olives, whereas regular olive oil is a blend, including both cold-pressed and processed oils, considered to be inferior in flavor, purity and appearance. A well-known example of fraudulent practice is adulterating fresh, pure virgin olive oil with inferior, cheaper olive oil or oils of another botanical origin.

How it works

Using a laser diode as a source light, the sample’s fluorescence emission is measured and 20 chaotic parameters from the resulting spectra have been calculated. Using these as independent variables of multi-parameter regression models, the concentration of adulterant can be estimated.

The structure of the sensor has been designed and developed by a 3D printer and its developers say the device “has the potential of being applied in situ for real-time and cost-effective analysis at oil mills or for quality control.”

The developers add that the tool is inexpensive both to manufacture and to operate. "Other clear advantages of our tool include the possibility of conducting on-site analyses, as the equipment is the size of a briefcase. Furthermore, it generates results in real time," commented José S. Torrecilla, a senior lecturer and researcher in the Department of Chemical Engineering & Materials at UCM.

The tool offers the olive oil sector a means to tackle an expensive problem. "The quality of olive oil is recognised nationally and internationally. It is therefore necessary to protect this quality and combat fraudulent activities carried out with increasing frequency and skill in the sector," added Torrecilla.

Chaotic algorithms

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

Subsequently, mixtures were made using oils with between 1 and 17 percent acidity that were also past their "best before" date. Lastly, measurements were performed using the sensor, which was manufactured via 3-D printing, and the results were analyzed using chaotic algorithms.

"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," concluded Torrecilla.