| Abstract
| - The main change found in the phenolic composition of virgin olive oils of Arbequina, Hojiblanca,and Picual varieties during storage in darkness at 30 °C was the hydrolysis of the secoiridoidaglycons. This reaction gave rise to an increase in the free phenolics hydroxytyrosol and tyrosol inthe oil. Filtration of oil and acidity influenced the hydrolysis to a large extent. Thus, the additionof commercial oleic acid to Hojiblanca and Picual oils increased the hydrolysis rate of the secoiridoidaglycons. In contrast, the concentration of lignans 1-acetoxypinoresinol and pinoresinol remainedconstant during storage. It must also be stressed that the total molar concentration of the phenoliccompounds analyzed in the oils changed slightly (<20% reduction) after one year of storage, whichis important from a nutritional point of view. However, the transformation of the secoiridoid aglyconsinto free phenolics may have consequences on oil taste and antioxidant capacity. Keywords: Olive oil; secoiridoid aglycon; hydrolysis; storage; phenolic
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