Olive oil genuineness
The K270 test provides useful information on the quality of the oil and on its degree of oxidation. It is distinguished from the other analyses you can perform on oil for an efficient quality control (Free Fatty Acids, Peroxide Value and Polyphenols) because it enables to identify rectified or different kinds of oils added to virgin olive oil and consent to escape from a fraud, in the worst case.
To define as best the oxidative condition of the oil and to remove any doubts about its genuineness it is necessary to determine parameters like K270, that measure the absorption of the ultraviolet light by the oily matter.
Natural oils that are mechanically extracted do not contain fatty acids chains formed by double or triple conjugated bonds. Typically these kinds of bonds (Fig. 1) create during rectification, that is the process in which the oil is mixed with other oils, refined or particularly old. They are not present in pure and freshly extracted olive oils.
Fig. 1 – Double bonds, Conjugated double bonds, Triple bonds, Conjugated triple bonds
The presence of these bonds in rectified oils makes them exhibit high UV absorbance values specifically in the 270 nm region, which are significantly higher if compared to those of virgin and extra virgin oils. Moreover ketone groups form during the most advanced oil oxidation stages, so that provoke a greater absorbance at 270 nm.
K270 helps to discover the great change that occurred in the oil structure and the parameter can be easily kept under control.
How to determine k270?
A simple reading of the oil at 270 nm is sufficient to perform the test. The so called coefficient of extinction (K) is measured and it gives the value of the k270 in the oil.
Spectrophotometers can perform the reading at 270 nm, and you can use the expensive and large instruments used by an equipped chemical laboratory or adopt the CDR OxiTester analysis system.
CDR OxiTester presents the following benefits in the performance of k270 test:
- Colour reading at 270 nm
- Reference method compliance
- Analysis of the sample as is
- Use of disposable and not expensive cuvettes, not quartz cuvettes
- Time test: immediate
- Up to 14 samples test sessions of analysis
- Ready to use and pre-calibrated supply
The graphic below shows the perfect correspondence between the reading with a laboratory spectrophotometer and the reading with the CDR OxiTester system.
In the table below you can see the different k270 values of some kinds of oils, showing how eloquent can be the parameter to identify a particular type of oil.
|Kind of oils||Extra virgin olive oils||Refined olive oil||Olive Pomace oil||Maize oil||Peanut oil|
|K270 values||< 0,20||0,65||1,3||2,00||7,90|