Improvement of oleuropein extractability by optimising steam blanching process as pre-treatment of olive leaf extraction via response surface methodology

► Optimisation of blanching in terms of oleuropein content and antioxidant activity of olive leaves extract was investigated. ► We improved the efficiency of extraction of oleuropein by 35 times compared to non-steam blanched olive leaves. ► The antioxidant activity of ethanolic extract of steam blanched olive leaves was improved by 13 times. ► The time required for a complete extraction, reduced from 24-48h to 1 h after multistage extraction process.