Fate of the phenolic compounds during olive oil production with the traditional press method

In the traditional press method for olive oil production, olives are crushed and malaxed into a paste, which is spread on mats. Pressure is applied to squeeze out the oil and wastewater, leaving a material on the mats called pomace. The oil and wastewater are then separated by gravity. The fate of the olive phenolic compounds, including oleuropein, and antioxidant activity was investigated at each stage of the process and the waste products (pomace and wastewater) were evaluated as potential sources of valuable phenolic compounds and antioxidant activity. The largest loss of phenolic compounds was seen at the crushing stage (60% of phenolic compounds, 70% of oleuropein) but only 21% of antioxidant activity was lost. Malaxation did not cause significant losses of phenolic compounds but the antioxidant activity was affected (43% loss). Pomace retained 26% of the phenolic compounds, 21% of the oleuropein and 33% of the antioxidant activity. When dried, the phenolic compounds and oleuropein were 3.5-fold concentrated in the wastewater and it exhibited a 2.7-fold increase in antioxidant activity compared to whole olives. The olive waste products from the traditional press method, pomace and wastewater, are good sources of valuable phenolic compounds and antioxidant activity.