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

Oils extracted from olive pastes by the direct centrifugation mode were compared with the homologous oils produced by the indirect centrifugation (after percolation) mode. The former were characterised by: (i) higher contents of total phenols, o-diphenols, hydroxytyrosol, hydroxytyrosol-aglycons, total volatiles, trans-2-hexanal and other pleasant volatiles, total tocopherols, total sterols and waxes; (ii) lower contents of triterpene dialcohols, aliphatic and triterpene alcohols, chlorophylls and pheophytins; (iii) lower values of integral colour index; (iv) higher values of turbidity, campesterol/stigmasterol ratio, 1,2-diglycerides/1,3-diglycerides ratio, oxidative stability and overall quality indices; and (v) higher sensory score. Stigmastadienes and trans-isomer C₁₈ fatty acids were always not detected. The average oil outputs of the two centrifugation extraction procedures were comparable, as confirmed by similar overall oil amounts found in the by-products. © 2000 Society of Chemical Industry.