In the last years, metallic crushers substituted granite stone mill with some variations in the organoleptic oil characteristics. To control the influence of the crushing method on the yield and oil quality, the olive pastes were obtained using three different ways: (i) new metallic crusher at mobile knives; (ii) granite stone mill; (iii) double olive crushing by the metallic crusher and the granite stone mill. With the aim to ascertain the useful use of a new metallic crusher (at mobile knives), experimental tests were carried out in an industrial oil mill. This oil mill is equipped by a centrifugal decanter generating two oil flows: first and second extraction (recovery) oils. The results showed that the yields obtained by different methods were satisfactory. No statistically significant differences have been observed in terms of oil yield and quality when different crushing devices were used. All first extracted oils are extra virgin with similar organoleptic characteristics, especially for the fruity intensity and for the bitter and pungent taste, as confirmed by the composition of volatile substances and the content of phenolic oil compounds. The recovery oils (second extraction oils) showed, in contrast to first extraction oils, a more intense green colour and a higher content of total phenols.Practical applications: Processing of sound olives with the right ripening grade and good quality allows to easily obtain an extra virgin olive oil, with commercial qualitative parameters according to the European Union requirements. However, different olive crushing systems affect the concentrations of some compounds responsible of aroma and taste (phenolic compounds). The use of the more violent metallic crushers facilitates obtaining oils with total phenol content higher than when using a stone mill. Here we used a particular metallic crusher (at knives) that, however, is suitable to replace the granite stone mill when a less pungent and bitter oil is required.

In recent years, in Italy, some large oil mills, equipped with centrifugal decanter at high loading capacity have adopted the complex diagram of the double extraction of oil and, in addition, have been supplied with suitable machine to recover part of stone fragments from olive pomace with the aim to reduce the costs. Our experimental tests were carried out in a large oil mill, located in Apulia region, which processes olives of Olea europaea L. “Coratina” cultivar by double centrifugation of olive pastes prepared by using the double crushing (millstones and metallic crusher) or the single crushing (metallic crusher). The results showed that the oil yield of the first extraction was high (between 85 and 86%), regardless to the method used for olive crushing. The quality of virgin olive oil of the first extraction was extra virgin with some differences due to the different batches of olives and, in part, also to the used crushing methods. The oil of the second extraction was recovered in a low quantity (0.3 kg/100 kg olives) and its composition was not normal only for the percentage of triterpene dialcohols. The recovery of stone fragments was satisfying (about 0.13 t/t olives) and helped to significantly increase the income of oil mill. Practical applications: The double extraction of oil, by the centrifugation system, and the recovery of SF allow to reduce the costs of olive processing in medium‐big sized oil mills. The second centrifugation, which permits to recover about 3 kg of oil/t of olives, and the recovery of SF, suitable to sell as fuel, allow to increase the income of oil mill. The double extraction of oil, by the centrifugation system and the recovery of olive stone fragments (SF) allow to reduce the costs of olive processing in medium‐big sized oil mills. The second centrifugation, which permits to recover about 3 kg of oil/t of olives, and the recovery of SF, suitable to sell as fuel, allow to increase the income of oil mill.