Phenolic compounds change during California-style ripe olive processing

Changes in phenolic composition of olive fruits (Olea europaea Intosso cv.) during California-style ripe olive processing were investigated. Hydroxytyrosol, tyrosol, oleuropein, oleuropein aglycones and oleoside-11- methyl ester were the main phenols identified by GC and GC-MS techniques. During the darkening process, only hydroxytyrosol decreased markedly and its diminution in flesh was directly related to the olive fruit browning development. Iron salts, used for colour fixation, seem to play a catalytic role in the oxidation of hydroxytyrosol and mechanisms involved in the browning are proposed.