Characterization of olive pomace extract obtained by cyclodextrin-enhanced pulsed ultrasound assisted extraction

Cyclodextrin enhanced pulsed ultrasound assisted extraction procedure was developed for obtaining olive pomace extract rich in bioactive polyphenols, principally oleuropein, tyrosol, and hydroxytyrosol. 20-minute extraction using 12 mm probe at 100% output intensity was selected as optimal for the extraction of olive pomace polyphenols, using 60% ethanol at 1:40 solvent to solid ratio. Addition of cyclodextrins to extraction solvent (especially randomly-methylatedbeta cyclodextrin and hydroxypropyl-beta cyclodextrin) significantly affected extraction yields, stability and the appearance (colour and particle size distribution) of obtained extracts. Extracts obtained under optimized conditions contained 887 mgkg-1 of hydroxytyrosol, 1117 mgkg-1 of tyrosol and 1744 mgkg-1 of oleuropein. In comparison to conventional solvent extraction, application of ultrasound-assisted extraction resulted in significantly higher yields, reduced extraction time and solvent consumption.