Utilization of olive pomace as a source of polyphenols:Optimization of microwave-assisted extractionand characterization of spray-dried extract

Olive pomace lags behind in significant amounts after production of olive oil. Although it contains various biologically active compounds, its potential as a valuable source of functional ingredients has not been fully utilized. The main reasons are shortages of existing extraction and drying methods that result in poor quality extracts, unsuitable for further testing and processing. In this study, optimal conditions for sustainable, fast and efficient microwave-assisted extraction of pomace phenols has been proposed. The proposed procedure is based on applying the power of 700 W for 10 min in a closed vessel system, using 20% ethanol as the extraction solvent. For ensuring satisfactory yields and powder characteristics during spray drying, hydroxypropyl-β-cyclodextrin was used and inlet temperature was set to 130 °C with the aspirator set at 100 %. Dry extracts obtained under optimized conditions contained significantly higher amounts of hydroxytyrosol (1 216 mg·kg-1) and showed improved antioxidant activity in β-carotene model system (214.7 g·kg-1) and DNA-scisson model system (minimal inhibitory concentration was 52.9 mg·l-1) in comparison to con- ventionally obtained extracts. Presented results enable objective assessment of the advantages of microwave extraction in processing olive waste into a functional food ingredient.