Abstract
In the last few years, a new term, “High-phenolic olive oil”, has appeared in scientific literature and in the market. However, there is no available definition of that term regarding the concentration limits of the phenolic ingredients of olive oil. For this purpose, we performed a large-scale screening and statistical evaluation of 5764 olive oil samples from Greece coming from >30 varieties for an eleven-year period with precisely measured phenolic content by qNMR. Although there is a large variation among the different cultivars, the mean concentration of total phenolic content was 483 mg/kg. The maximum concentration recorded in Greece reached 4003 mg/kg. We also observed a statistically significant correlation of the phenolic content with the harvest period and we also identified varieties affording olive oils with higher phenolic content. In addition, we performed a study of phenolic content loss during usual storage and we found an average loss of 46% in 12 months. We propose that the term high-phenolic should be used for olive oils with phenolic content > 500 mg/kg that will be able to retain the health claim limit (250 mg/kg) for at least 12 months after bottling. The term exceptionally high phenolic olive oil should be used for olive oil with phenolic content > 1200 mg/kg (top 5%).
Highlights
IntroductionOlive oil is considered as a healthy fat due to the high content of monounsaturated lipids and the presence of phenolic ingredients with several health preventive bioactivities
Olive oil is considered as a healthy fat due to the high content of monounsaturated lipids and the presence of phenolic ingredients with several health preventive bioactivities.Olive oil, apart from having a beneficial lipid composition for human health, is an excellent source of phenolic substances with excellent health protection properties.European Regulation 432/2012 distinguishes olive oils in terms of their effect on health, depending on their content of these substances [1]
The term oleuropein and ligstroside aglycon correspond to the monoaldehydic closed ring forms 5a,b and 6a,b and the term dialdehyde oleuropein and ligstroside aglycon correspond to the open ring dialdehydic forms 7a,b and 8a,b which are in equilibrium with the monoaldehydic enolic forms 9 and 10, respectively
Summary
Olive oil is considered as a healthy fat due to the high content of monounsaturated lipids and the presence of phenolic ingredients with several health preventive bioactivities. A study by LCMS on laboratory produced olive oils reported minimum and maximum values of individual phenolic compounds in a study of 160 samples from 80 cultivars [33] and the most recent study of 44 varieties monitored for three years with the same methodology showed a diverse total phenolic content ranging up to 4497 mg/Kg [34]. All the above-described approaches show us that to define the term “high-phenolic olive oil”, it is necessary to obtain results from a large number of industrially produced samples recorded during a long period of several years and analyzed by the same methodology For this purpose, we performed a statistical evaluation of the phenolic content of the olive oil samples that have been recorded since 2009 in the olive oil database of the Laboratory of Pharmacognosy of the National and Kapodistrian University of Athens, that was significantly enriched by the Interreg-Med “ARISTOIL” project during 2016–2020. The results of the statistical evaluation in combination with the results of the storage study were used to provide a first definition of the term “high phenolic olive oil”
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