What is absorbance
If you have stopped to read some olive oil labels, you may have come across terms such as UV spectrometry, Delta K, K 270, K 232... These are data that reveal the absorbance index to ultraviolet light. You're just as confused, right? Therefore, in this post we explain What is absorbance in olive oil and how to interpret it.
What is absorbance and what is it for?
To answer what absorbance is in olive oil, it must first be noted that, in general terms, the absorbance to ultraviolet light is a measurement used in chemistry and spectroscopy that allows determining the concentration of a substance in a liquid sample. Specifically, it evaluates the ability of an element to absorb light at a specific wavelength.
In the oleic sector, absorbance is used to determine its quality and purity. In fact, it is one of the chemical parameters officially used in the evaluation of the different categories of olive oil, along with the degree of acidity and the peroxide value. Because? When light passes through an EVOO sample, some components present in the oil can absorb some of the light. This results in a reduction in the intensity of the transmitted light. Thus, the amount of substances present in olive oil that can absorb light can be quantified.
What relationship exists between the absorbance index and the quality of EVOO?
The relationship is simple: The greater the amount of substances, the greater the degree of absorbance and the lower the quality and purity.. Thus, an olive oil with a high absorbance will contain more impurities and, therefore, its quality will be lower. On the contrary, a low absorbance index will denote that we are facing a quality EVOO, without unwanted compounds and with good resistance to oxidation.
How is oil purity measured?
To carry out a study of what the absorbance is in olive oil, the UV-Visible spectrophotometry technique in which three factors are assessed: the K 270 index, the K 232 and the Delta-K.
What does the K 270 index indicate?
El índice K 270 está dirigido a detect oxidative state that the product presents, that is, the ability of the olive oil to remain without losing properties for a longer time (because expiring, you know, that does not expire).
In particular, it measures the absorbance of the oil at the wavelength 270 nanometers. As you can imagine, the higher the K 270 index, the greater the oxidation and the lower the quality. Furthermore, by applying this wavelength, secondary compounds can be seen that would not appear in the peroxide index test. Hence, both systems complement each other to examine the degree of oxidation and the olive oil stability.
What does the K 232 factor evaluate?
In this case, the 'modus operandi' is the same as in the previous index, except for the wavelength to which the olive oil is subjected. Instead of 270 nanometers, ultraviolet light is located at a distance of 232 nanometers.
This adjustment allows us to discover the presence of hydroperoxides and conjugated dienes or, so that we understand each other, assesses the initial oxidation of the oil. Consequently, high values of the K 232 factor indicate low quality and vice versa.
What is Delta K?
Finally, within the absorbance in olive oil, there is the Delta K test. It is a measurement aimed at evaluating the purity index of the product and the possible mixture with refined oils. It is very important to know if an EVOO has been adulterated..
So, If the compounds called conjugated trienes detected by Delta K appear reflected in the test, we would be looking at a refined oil.. On the other hand, these impurity peaks are not observed if the oil is pure extra virgin.
What is the absorbance of extra virgin olive oil?
In addition to knowing what absorbance is in olive oil, surely now you are wondering what the levels that a quality oil must present within UV spectrometry. Well, you should know that the limits are regulated by the community regulations. As regards extra virgin olive oil, the absorbance values cannot exceed the 0.22 in K 270; 2.50 in K 232; and 0.01 in Delta K.
Also, if you want to check it, it is possible that This information is included on the label. Since 2002, the olive oil marketing standards They allow indicating the degree of acidity of an oil if it is accompanied by data on the peroxide index, wax content and ultraviolet absorbency. Although it is not mandatory. That's why, for reliable verification, that of your palate. Try any variety of the Premium EVOO from Hacienda Guzmán and you will not need spectrometry to confirm that it is a top quality extra virgin olive oil.
