A comparative study of UV spectrophotometric methods for detection of olive oil adulteration by refined oils

UV spectrophotometric measurements on hundreds of virgin olive oils and refined vegetable oils have shown that a previous method for evaluating the absorption maxima at 315 nm by calculation an Rs value (ratio of slopes of absorption curve in both sides of 315 nm) may lead to false conclusions concerning possible adulteration of virgin olive oils by refined olive, olive residue or seed oils. It was found that ΔK3154% values, obtained directly from the UV spectra, are much more reliable estimates of conjugated tetraene absorption at 315 nm, without affecting the sensitivity of the method. © 1990 Springer-Verlag

Detection of adulteration of olive oil with seed oils by a combination of column and gas liquid chromatography

Samples of virgin olive oil and refined seed oils, as well as mixtures of olive oil with 10 and 5% seed oils were fractionated by column chromatography on silicic acid impregnated with ammoniacal silver nitrate. It was possible to isolate a characteristic fraction enriched in polyunsaturated triglycerides. Its linoleic acid content in pure olive oil never exceeds 9.3%, whereas in pure seed oils, it varies between 38.1 and 70.1%; in mixtures of olive oil with 10 and 5% of seed oils, the respective values are 22.3-38.2% and 15.6-32.1%. The oleic-to-linoleic acid ratios of the same fraction are more than 7.6 (olive oil), 0.2-0.8 (seed oils), 1.1-2.0 (olive oil with 10% seed oils) and 1.4-3.6 (olive oil with 5% seed oils). These analytical values may be used as a safe criterion for the eventual adulteration of olive oil with seed oils. © 1981 American Oil Chemists' Society