Double oil extraction from olive paste and olive pomace by centrifugal decanter at 2-phases, type integral

Tests were carried out in an industrial olive oil mill to olive process by the double extraction of olive pastes and fresh olive pomace, using 2 centrifugal decanters at 2-phases, type integral, that do not need water addition. Results obtained showed that the average oil yield of the first extraction was higher than 83% and the average oil yield of the second extraction was 3.6%. Therefore, using the double extraction it was possible to obtain an average oil yield of 87% of that contained in the olive paste. The oil obtained by the centrifugation of the olive paste had better qualitative characteristics with respect to those of the oil obtained by the centrifugation of fresh olive pomace. However, the total phenol content was higher in the oils extracted from fresh olive pomace because it was heated at 60 °C during the malaxation, favouring the increase of the solubility of the phenolic substances in the oily phase. The content of the C5 volatile compounds of the head space was higher in the oils obtained by the centrifugation of olive pomace, while in the same oils the content of the C6 volatile compounds was lower. Finally, the percentage of triterpene dialcohols (erythrodiol and uvaol) and the content of waxes and aliphatic alcohols of the oils obtained by the centrifugation of fresh olive pomace were, in some cases, higher than the limit values established by the UE law.