Supercritical fluid extraction for enhancing polyphenolic compounds production from olive waste extracts.

BACKGROUND A number of residues are produced during the olive oil extraction process, such as crushed pits, olive leaves, pomace and exhaust olive pomace. In addition, pruning of olive trees results in a huge amount of biomass. All of these lignocellulosic materials constitute a source of energy and chemicals that can be used as raw materials in biorefineries. Among them, antioxidants are of particular interest due to their potential applications in pharmaceutical and food industry. RESULTS: Supercritical fluid extraction (SFE) was applied on three different olive residues – pruning biomass, leaves and exhaust pomace. In this, 60% ethanol was used as cosolvent at three different pressure levels, 200, 250 and 300 bar. The best conditions for each residue were determined and compared with conventional extraction. Results show that 300 bar was the best pressure for SFE in terms of antioxidant activity of the extracts. The main polyphenolic compounds also were identified, among which hydroxytyrosol, chlorogenic acid, caffeic acid and ferulic acid were present. CONCLUSION: SFE at 300 bar proved to be the best option for obtaining a high‐activity antioxidant extract from olive leaves, exhaust pomace and pruning biomass, with hydroxytyrosol the prominent compound detected. This procedure could be integrated in a biorefinery based on olive‐derived biomass. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]