Subcritical treatment of olive oil: Minor phenolic composition and antioxidant properties of the solvent extracts

Olive oil extracted from four exotic olive cultivars was subjected to subcritical treatment using green and organic solvents. The minor phenolic compounds were identified and quantified by RP-HPLC-DAD. Significant (p <= 0.05) variation in the phenolic compounds and antioxidant properties was observed with respect to cultivar, solvent and the extraction conditions. For the methanolic and ethanolic extracts, the antioxidant properties generally increased upon subcritical treatment but decreased drastically for subcritical water extraction. Besides correlation among hydroxytyrosol, tyrosol and oleuropein, the multivariate analysis revealed high correlation of antioxidant properties with hydroxytyrosol, oleuropein, tyrosol and apigenin. The principal components analysis (PCA) revealed two components explaining 86.6% variability. PCA separated aqueous and organic solvents both at ambient and subcritical conditions in the score plot. The loading plot exhibited maximum positive loadings of the analyses. It is concluded that subcritical water extraction could be manipulated for the recovery of oleuropein and hydroxytyrosol from olive oil.

Automated summary

The study examined the effects of subcritical treatment with green and organic solvents on olive oil extracted from four exotic cultivars. The research found significant variations in phenolic compounds and antioxidant properties depending on the cultivar, solvent, and extraction conditions. Subcritical water extraction showed a drastic decrease in antioxidant properties, while methanolic and ethanolic extracts generally increased in antioxidant properties after subcritical treatment.