Evaluating two kinds of centrifuged virgin oils arising from continuous olive processing

Oils extracted from olive pastes by the direct centrifugation mode were com pared with the homologous oils produced by the indirect centrifugation (aft er percolation) mode. The former were characterised by: (i) higher contents of total phenols, o-diphenols, hydroxytyrosol, hydroxytyrosol-aglycons, to tal volatiles, trans-2-hexanal and other pleasant volatiles, total tocopher ols, total sterols and waxes; (ii) lower contents of triterpene dialcohols, aliphatic and triterpene alcohols, chlorophylls and pheophytins; (iii) low er values of integral colour index; (iv) higher values of turbidity, campes terol/ stigmasterol ratio, 1,2-diglycerides/1,3-diglycerides ratio, oxidati ve stability and overall quality indices; and (v) higher sensory score. Sti gmastadienes and trans-isomer C-18 fatty acids were always not detected. Th e average oil outputs of the two centrifugation extraction procedures were comparable, as confirmed by similar overall oil amounts found in the by-pro ducts. (C) 2000 Society of Chemical Industry.