The antioxidant capacity of polyphenols has an important role for olive oil stability since it exist a correlation between the quantity of total polyphenols and the resistance to oxidation over time. Polyphenols perform a protective action not only on oil but also on the cells of the human being since they oppose the negative effect of free radicals (anti-age).The quantity of polyphenols contained in oil depends on the type of cultivar, the harvesting period, the characteristics of the soil and the extraction process.
The Total Polyphenols test permits to verify the quality of oil but also to intervene with the extraction process, modifying the parameters that weight negatively on the final content of the substance; for example it is highly penalizing adding water to the olive paste since polyphenols are hydrosoluble substances.
Here are the answers to some common questions about these components of olive oil that are not always adequately assessed
FAQ about Polyphenols in olive oil and total Polyphenols test
1. What are polyphenols?
Polyphenols are chemical substances characterized by one or more oxydrilic groups on the benzenic ring.
2. Why are polyphenols important parameter for oil?
They perform a protective action on oil oxidation generated by oxygen. They are consumed preserving oil from oxidation. In addition to that, as described in many studies, they made a powerful antioxidant action also on our body.
Quantifying their value has a relevant importance as an aid for the verification of the correctness of the productive process and for making useful expedients to preserve the highest concentration.
3. How many polyphenols are present in oil?
Many types of polyphenols are present in olive oil (around 15). Each of them has a different reactivity.
4. Does it exist an official method to measure the total content?
The only official method is the chromatographic method (HPLC); the method requires the separation of the different phenolic components; in addition, requiring very expensive instrumentations, it is needed a laboratory and a specialized user, generally a chemist. The analysis duration is very long.
5. Does it exist an alternative method?
A method commonly used is the colorimetric method Folin-Ciocalteau. Anyway, this method has many variations; each of them brings to results sensibly different from one laboratory to another.
Practically it is very difficult to compare the values obtained by different laboratories.
CDR Foodlab® method, implemented also in the CDR OxiTester analyzer, has been developed to give the highest reliability simplifying the analysis execution. The test does not need specialized personnel and the analysis duration (around 5 minutes) is extremely lower than that of the other methods, especially Folin-Ciocalteau method.
6. Which is the principle of the analysis used in CDR Foodlab®/CDR OxiTester method?
The antioxidant action of polyphenols of the oil is marked using a specific reagent. The oil, reacting with the free radicals present in the reagent determines its decolorization. The entity of this change in the colour is measured by the instrument and, thanks to the correlation present between the value measured and the polyphenols concentration, it is shown the total polyphenols value. The method imitates into the cuvette the action that polyphenols perform against the free radicals of the oil and it quantifies their efficiency. The result is expressed in mg/Kg of tyrosol. The great potentiality of the system, in addition to the extreme simplicity of use, is the possibility to compare data in a very simple way. Moreover it can be used for monitoring the production and increase its quality.
7. CDR FoodLab®/CDR OxiTester method is comparable with the offical method?
CDR Foodlab® analytical system has been correlated with COI/T.20/DOC. 29 – 2009 – DETERMINATION OF BIOPHENOLS IN OLIVE OILS BY HPLC official method, during a study conducted by the by the Commodity Chemical Laboratory of Chamber of Commerce of Florence, Italy. As shown on the graphic, it has obtained very good results.
8. Is the determination of the amount of polyphenols carried out with CDR OxiTester useful to establish the shelf-life of virgin and extra-virgin olive oil?
To establish the shelf-life of an olive oil, it is necessary to determine its oxidative stability. The official method used to measure this parameter consists in determining the stability index of an oil with a method commonly known as Rancimat.
In a study conducted by Minerva S.A. and Asteriadis S.A. in collaboration with the University of Athens, researchers compared the Rancimat and CDR OxiTester methods for the determination of the amount of polyphenols.
The study published in the Journal of AOAC International states that the two methods show a good correlation: thus CDR OxiTester represents a valid alternative to the Rancimat method to measure the stability index of virgin and extra-virgin oils and consequently to determine the shelf-life of a product. In addition, the testing time of the CDR OxiTester method is significantly shorter as compared to the time required with the Rancimat method.
Testing time with CDR OxiTester – Approximately 6 minutes
Testing time with Rancimat – On average 10 – 12 hours