Testing For Purity
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. 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.
Read more about this topic: Olive Oil Regulation And Adulteration
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