Even though there are regulations in place, there will always be suppliers who attempt to market low grade olive oil as a more expensive higher grade or to substitute a portion of the olive oil with cheaper oil such as rapeseed or sunflower.

Using a number of analytical tests, set up out in European Union Regulation 2568/91 (see latest guidance from Rural Protection Agency), RSSL can detect whether cheaper oils have been used to dilute pure olive oil.  The Regulation and its amendments sets out over 20 analytical values for determining grade, quality and authenticity of an olive oil.  Most edible plant based / vegetable oils are a complex mixture of the main components called triglycerides. The triglycerides are composed of fatty acids that are found in proportions often characteristic of the particular oil. There are also lower / minor amounts of di- and monoglycerides, free fatty acids, trans fatty acids, sterols, waxes, flavonoids; and a variety of other organic molecules. 

The different analytical tests can be used to provide different information, for example, the fatty acid profile, sterol profile, triglyceride analysis and glyceryl 2-palmitate determination can be used to detect the presence of oils other than olive.  Erthyrodiol, uvaol, wax and stigmastadiene analysis are used to detect the presence of olive-pomace oil and/or refined oil in virgin olive oils.  Peroxide value, free fatty acids and UV determination are often used to determine the quality of the olive oil and ensure it is the correct grade.

The tests required can be broadly categorised as:

  • Free-fatty acids – measured by total acidity and indicates quality
  • Peroxide value – measures the oxidation of the oil determined by peroxide value.  A high value indicates a poor quality, older or mistreated oil.
  • UV determination – assess oxidation and indicate the presence of a refined olive oil in virgin oil.
  • Fatty acids – used as an indicator of purity or the presence of oils other than olive oil
  • Glyceryl 2-palmitate – high levels of saturated fatty acids at the 2- position are indicative of adulteration with an interesterified oil.
  • ECN42 - measuring the level of triglyceride trilinolein and similar triglycerides.
  • Sterols - used as an indicator of purity or the presence of oils other than olive oil
  • Waxes and diols – levels of waxes and erythrodiol / uvaol are higher in solvent-extracted olive oil (olive pomace oil or olive residue oil) than in olive oils.
  • Stigmastadienes - indicates whether the oil has been refined.  High levels indicate the presence of cheaper refined oil in virgin olive oil
  • Taste – helps indicate age, quality and rancidity.

RSSL is also able to investigate the suspected adulteration or help assess the authenticity of expensive speciality oils; such as evening primrose, walnut, almond and wheat germ; and also animal derived fats such as milk fat. RSSL also has a lot of experience of determining the level of different oils and fats in blends and in finished products.

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