Polyphenolic profile and antioxidant activity of olive mill wastewater from two Sicilian olive cultivars: Cerasuola and Nocellara etnea

During the last years, there has been an increasing interest in the valorization of the food-processing side streams due to their potentially valuable phytochemical content. Olive mill wastewater (OMWW), the main by-product of olive oil extraction process, are rich in polyphenolic compounds, widely known for their health-promoting benefits. However, different parameters—such as the distinct olive cultivar, ripeness of the fruit, processing techniques, climate, and storage conditions—play an important role in determining the specific quali-quantitative polyphenolic composition of OMWW. In this work, for the first time, we have characterized and compared the polyphenolic profile of different OMWW generated by centrifugal three-phase olive oil mills processing of two important Sicilian cultivars, Cerasuola and Nocellara etnea. Moreover, the correlated antioxidant activity and the stability of both OMWW samples stored at different conditions were evaluated. Our results show that even if OMWW are characterized by different and individual polyphenolic profile, both side streams have high levels of antioxidant activity. From a comparative point of view, we found that Cerasuola-OMWW showed higher values of total phenols (5.20 ± 0.21 g/l gallic acid), total flavonoids (2.28 ± 0.23 g/l catechin) and hydroxytyrosol content (821.86 ± 0.01 mg/l) respect to the analog parameters measured in Nocellara etnea-OMWW; these phytochemical values showed a significant stability in both OMWW samples stored at −20 °C for 6 months. Conversely, a decrease in the level of these compounds was observed in samples maintained at 4 or 25 °C for 45 days.