28 Nov 2003
An optical technique that identifies the type and origin of an olive oil, could protect producers and consumers from fraud.
The popularity of the Mediterranean diet means that the production of premium extra virgin olive oil is now big business. And it’s a business opportunity that has not gone unnoticed by fraudsters who try to pass off cheaper low-grade oils as expensive Italian brands made in Tuscany.
To help combat the problem, scientists from Italy and UK teamed up to develop an optical system that can check the authenticity of an oil.
The system, developed by Italy’s CNR Institute for Applied Physics in Florence and the CNR Trees and Timber Institute in Sesto Fiorentino as well as Loughborough University, UK, relies on spectroscopy and light scatter.
Anna Grazia Mignani and her coworkers discovered that by performing white-light absorption spectroscopy and scatter measurements on an oil sample at several different angles it is possible to monitor both the color and turbidity of the oil.
The system, described at Photonics East last month, consists of four white light sources (450 to 630 nm) placed around the sample and an optical fibre spectrometer.
The result of the measurement is a distinctive optical fingerprint that reveals an oil’s grade (virgin or extra-virgin) and its region (approved olive groves in Tuscany or elsewhere).
To test the technique, the researchers used principal component analysis (PCA) to classify the optical fingerprints from more than 100 different samples of olive oil. Sure enough, all the extra-virgin olive oils made from the same harvest in Tuscany were clustered together.
Oliver Graydon is editor of Optics.org and Opto & Laser Europe magazine.
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