page_title: Olive oil regulation and adulteration
section_title: Testing for purity
hierarchical_section_title: Olive oil regulation and adulteration / Testing for purity
caption_attribution_description: Italiano: Valentina Domenici, assessore al Comune di Rosignano Marittima, ricercatrice scientifica, divulgatrice scientifica. Qui al lavoro presso il Dipartimento di Chimica e Chimica Industriale, a Pisa (analisi di oli di oliva)
context_page_description: Olive oil regulation and adulteration are complex issues overseen and studied by various governmental bodies, non-governmental organizations, and private researchers across the world.
context_section_description: The detection of olive oil adulteration is often complicated with no single test that can accomplish the task. A battery of tests is employed to determine olive oil authenticity and identity of the adulterant. Included in this testing regime is the determination of free acidity, peroxide value, UV extinction, fatty acid composition, sterol composition, triglyceride composition, wax content, steroidal hydrocarbons, and the Bellier test. Methods employing chromatography/mass spectrometry and spectroscopy are often used to detect adulteration of olive oil These methods can be very expensive, time consuming, and results are often incomplete, since components added/substituted can not always be identified.
  Test results are measured against the International Olive Council trade standard to identify abnormalities. Each test provides key information which allows a decision to be made with respect to the grade of Olive oil and the identity of any adulterants. However, the International Olive Council does not test for deodorisation which makes up the bulk of fake extra-virgin oils. Soft column deodorisation is the process where steam is forced through a tank of inferior oil which removes all taste, colour and nutrients, colouring is then added before the tank is topped up with real extra-virgin oil to add flavour.
  A test published in 1887 described the detection of olive oil adulterated with mineral oil by a simple titration of the carboxylic acid moieties present in natural vegetable oils.  The procedure involved boiling 10 milliliters of olive oil with 40 milliliters of approximately 1 molar potassium hydroxide in 95% ethanol, adding water to 100 grams to dissolve the saponified lipids, and titrating against a normal sulfuric acid solution using phenolphthalein as a pH indicator dye.  The base stock solution was titrated to neutralize an equal quantity of the acid, so without the presence of vegetable oil it would require 40 milliliters of acid to cause a color change, but in the pure oils tested (almond, benne, cottonseed, cod liver oil, linseed oil, and olive oil, only 6 milliliters were required.  In accordance with this, olive oil adulterated with 10% mineral oil required 8 milliliters, and with 20% 11 milliliters.  The adulterated oil tested in 1887 required 14 to 17 milliliters to neutralize, so it might have been 30–40% mineral oil.
  Olive oil DNA analysis methods, based on the use of polymerase chain reaction (PCR) (e.g. DNA fingerprinting), have been use for determining counterfeit. These techniques requires extensive sample preparation, which needs specific optimization to ensure extraction of sufficient DNA, and that PCR inhibitors are not affecting the analysis. To date, there is no DNA extraction method applicable to any sample.
  Another method against olive oil adulteration, making use of artificial, sub-micrometer-sized DNA barcodes, has recently been developed. The barcodes consist of magnetically recoverable silica particles containing synthetic DNA sequences, which are added to the oil in very small amount (down to 1 ppb) and can be retrieved at any time for authenticity test by PCR/sequencing. The advantages of this method, compared to conventional techniques, are that it is low-cost, sample preparation is minimal and requires minute volumes, and the method is universal, since it can be applied to any oil type/sample without specific procedure optimization.
caption: UV-Vis spectroscopy analysis of olive oil samples in an Italian laboratory
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