A New Definition of the Term “High-Phenolic Olive Oil” Based on Large Scale Statistical Data of Greek Olive Oils Analyzed by qNMR

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%).

Virgin Olive Oil Phenols, Fatty Acid Composition and Sensory Profile: Can Cultivar Overpower Environmental and Ripening Effect?

“…In our study in Oblica, oils produced at laboratory scale TPC values varied from 185.0 to 760.3 mg/kg (average 436.7 mg/kg) while, for Leccino oils, values varied from 118.9 to 641.76 mg/kg (average 337.74 mg/kg) ( Figure 2 ). These results are in line with studies showing different phenolic content in monocultivar oils that ranges from 40 to more than 4000 mg/kg [ 17 , 29 , 55 , 56 , 57 ].…”

A Study on the Clustering of Extra Virgin Olive Oils Extracted from Cultivars Growing in Four Ionian Islands (Greece) by Multivariate Analysis of Their Phenolic Profile, Antioxidant Activity and Genetic Markers

“…The same trend was observed for oleacein. The Kerkyra_Lianiolia mean values are in line with those reported recently by Diamantakos et al [ 20 ], who studied 5674 samples from over 30 Greek varieties.…”

“…Recently, oleaceinic and oleocanthalic acid were added to the list of secoiridoid acids that are considered standard components of EVOO [ 17 , 18 ]. Therefore, the characterization and quantitative determination of olive oil polyphenols is extremely important to stakeholders [ 19 ], and as a result there has been an increased interest in the systematic characterization of the total concentrations of polyphenols, or of the individual compounds, with special attention given to the presence of oleacein and oleocanthal in olive oils mainly from Spain, Italy, and Greece [ 15 , 20 , 21 , 22 , 23 , 24 , 25 ].…”

“…Numerous factors affect the phenolic concentration of extra virgin olive oil, such as olive cultivar and fruit maturation, agronomic and environmental factors, processes used for olive oil extraction, packaging conditions, storage conditions, and shelf-life [ 20 , 26 , 27 , 28 ]. The above factors introduce variation to the phenolic profile of olive oils extracted even from the same cultivar.…”

“…In addition, several analytical factors further complicate the comparison of the phenolic composition between olive oils. These include on one hand the numerous different methods used to determine and quantify the phenols, such as gas chromatography coupled with mass spectrometry; high performance liquid chromatography with electrochemical, mass spectrum (MS), ultraviolet (UV), diode array, or fluorescence detectors; 31 P-NMR (nuclear magnetic resonance) and 1 H-NMR spectroscopy [ 15 , 20 , 21 , 26 , 28 , 29 , 30 ]; and on the other hand, non-uniformity in the concentration units which are reported mainly as caffeic acid equivalents, gallic acid, or tyrosol equivalents. Therefore, the accurate determination of the secoiridoid compounds remains challenging.…”