Polyphenols and quality of virgin olive oil in retrospect

Polyphenols influence the oxidative stability and sensory quality of virgin olive oil. Studies from the last 30 years are reviewed and the most significant findings are presented. Information is given on the main phenolic compounds detected and identified in olive fruit and oil. In recent years powerful analytical techniques (GC-MS, HPLC-MS, NMR) have been used to investigate the complex nature of olive oil polyphenols. Tyrosol, hydroxytyrosol, oleuropein aglycon and their derivatives with a non-phenolic acid and elenolic acid in free or esterified forms are the main components of the water-methanol extract of virgin olive oil, known as the polar fraction. Total phenol content as determined colorimetrically correlates well with the oxidative stability of the oil. The contribution of individual phenols to oil stability has not been fully investigated. There is still more to be known about the importance of the presence of phenolic components to the sensory quality of the oil.