Study of phenolic compounds in virgin olive oils of the Picual variety
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Monovarietal Picual olive oils possibly represent 25% of the world's olive oil production. HPLC was used to analyse phenolic compounds and tocopherols in Picual olive oils obtained during two successive crop seasons (1999/2000 and 2000/2001) and from different geographic areas of the Jaén province, which is located in the south of Spain. Oils obtained at the beginning of each season had a higher content of each phenolic compound than those obtained at the end, although this effect was more pronounced for orthodiphenols than for non-orthodiphenols. The main phenolic compound detected in this monovarietal oil was the aglycon of oleuropein followed by the other secoiridoid aglycons. Lignan concentration in oil showed low variability with season and harvesting time, and pinoresinol in particular was present at a concentration of about 40 ppm. Therefore, the total polyphenol content of this monovarietal oil ranged from 300 to 700 ppm. Similarly, significant differences in these compounds were not detected between geographic areas. This monovarietal oil is very stable due to its high content of oleic acid and for this reason, the storage of oils for 2 years in amber glass bottles caused only a 30% decrease in phenolic compounds. An increase was found in simple phenols such as hydroxytyrosol and tyrosol liberated from the acid hydrolysis of the secoiridoid aglycons, and minor losses in tocopherols were also observed. These data provide a basis for the evaluation of polyphenol intake from virgin olive oil consumption, particularly from the monovarietal olive oil most consumed in the world.
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