Phenolic content and antioxidant activity of olive by-products and antioxidant film containing olive leaf extract

• 28 phenolic compounds were identified in olive leaf (OL) and cake (OC) by UPLC-Q-TOF-MS.
• Phenolic composition depends on the extraction solvent.
• OL is the most efficient antioxidant by DPPH assay and ORAC method.
• 78% of free radicals were scavenged by the material containing 10% of leaf extract.
• Migration of phenolic compounds of OL was below the limit of detection.

The antioxidant activity of olive leaf (OL) and cake (OC) extracts with different solvents was evaluated. 70% of aqueous ethanol extract of OL was chosen as the most antioxidant extract based on antiradical activity (DPPH) (95.4 ± 0.3%) and oxygen radical absorbance capacity (ORAC) (0.82 ± 0.07 g equivalent Trolox per g of solution) assays. This OL extract was incorporated in two multilayer materials consisting of (i) polyethylene/polyethylene (PE/PE) film and (ii) polyethylene/paper (PE/P). These multilayers were exposed to a gas stream enriched in free radicals to evaluate the scavenging capacity of both materials. PE/PE film exhibited the highest scavenging activity of free radicals (78.8%). Migration of the phenolic compounds from olive by-products into two simulants was performed and demonstrated a non-migrating behavior. The limits of detection and quantification for oleuropein were 0.5 μg kg−1 and 1.7 μg kg−1 and for Luteolin-7-O-glucoside 1.3 μg kg−1 and 4.3 μg kg−1 respectively.