First and second centrifugation of olive paste: influence of talc addition on yield, chemical composition and volatile compounds of the oils

Second centrifugation of olive paste is often carried out to recover the residual oil of the olive paste, leading to a product that must be marketed as raw olive pomace oil. An experimental investigation was carried out to assess yield, chemical composition, and volatile compounds of oils obtained after the first and the second centrifugation of olive paste. Olives from Coratina cultivar were used in trials and were processed by adding 1 g/100 g and 2 g/100 g of technological coadjuvant micronized talc, as well as without talc addition, as control. The obtained results evidenced that the second centrifugation determined a significant decrease of residual oil in pomace. The addition of talc determined a significant increase of oil yield respect to control without talc, but only after the first centrifugation. A scarce increase of oil yield was observed after the second centrifugation, in presence of talc, that would render economically not viable the use of a second working line. Moreover, the oil obtained after the second centrifugation showed higher extent of oxidative and hydrolytic degradation than the oil from the first centrifugation. Some volatile compounds, derived from oxidative and fermentative phenomena, were observed in specific amounts in the oil of second centrifugation.