The use of gamma radiation for extractability improvement of bioactive compounds in olive oil wastes

Olive pomace is an environmentally detrimental waste from olive oil industry, containing large amounts of bioactive compounds that might be used by the food industry. In this work, the effects of gamma radiation on phenolic compounds and bioactive properties (antioxidant, antimicrobial activities and hepatotoxicity) of Crude Olive Pomace (COP) and Extracted Olive Pomace (EOP) extracts were evaluated. Hydroxytyrosol was the main phenolic compound identified in both olive pomace extracts (24–25 mg/g). The gamma radiation treatment of olive pomace improved at least 2-fold the extractability of phenolic compounds. Moreover, results suggested that gamma radiation at 5 kGy increased the antioxidant activity in EOP, while keeping the ability to protect erythrocytes against oxidation-induced haemolysis. Gamma radiation at 5 kGy could be a suitable technology for olive oil pomaceswaste valorization, contributing to enhance extraction of phenolic compounds and bioactive properties, especially when applied on extracted material.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support to C2TN UID/Multi/04349/2019, CIMO UID/AGR/00690/2019, J. Madureira [SFRH/BD/136506/2018]; L. Barros, J. Pinela and M.I. Dias thank the national funding by FCT, P.I., through the institutional scientific employment programcontract; FEDER-Interreg España-Portugal program for financial support through the project 0377_Iberphenol_6_E; “UCASUL - União de Cooperativas Agrícolas do Sul” agro industrial cooperative for providing the samples; to Technological Unit of Radiosterilization (University of Lisbon) for the samples irradiation; and to Molecular Materials Synthesis Laboratory (responsible Researcher Dr. Dulce Belo, C2TN) for the solvent evaporations.