PHENOLIC-COMPOUNDS RELATED TO THE BLACK COLOR FORMED DURING THE PROCESSING OF RIPE OLIVES

The composition in phenols of olive, the changes they undergo during the processing of ripe olives, and their relationships with surface color development were studied. The main phenols of these olives are identified as hydroxytyrosol (3,4-dihydroxyphenylacetic acid), verbascoside, tyrosol, vanillic acid, p-coumaric acid, and oleuropein. After the sodium hydroxide treatment, they are hydroxytyrosol, tyrosol, vanillic acid, caffeic acid, and p-coumaric acid. During the darkening process only the o-diphenol compounds hydroxytyrosol and caffeic acid are transformed, and their content diminution in flesh is directly related to the surface color or the surface color development. Thus, they are considered to be the promoters of the dark color obtained during the traditional ripe olive processing.