RP-UHPLC-DAD-QTOF-MS As a Powerful Tool of Oleuropein and Ligstroside Characterization in Olive-Leaf Extract and Their Contribution to the Improved Performance of Refined Olive-Pomace Oil during Heating.

Since olive leaf is a potential source of phenolic fraction that is assumed to have good antioxidative effects, we purposed to add its extract to the refined olive-pomace oil during heating to increase its oxidative stability. RP-UHPLC-DAD-QTOF-MS was employed to characterize the phenolic fraction.The oil samples were evaluated by measuring the polymers and the polar compounds and thus detecting specific oxidized compounds. Using this approach, the results showed that incorporating olive leaf extract in refined oil significantly reduced the formation of polymers from 14.39% to 10.45% and the oxidation state by the variation of extinction ΔK from 3.02 to 2.29 during 20 h of heating compared to unenriched oil. This study has proven that the use of natural substances is an opportunity to extend the life of refined oils.

Effect of addition of olive leaves before fruits extraction process to some monovarietal Tunisian extra-virgin olive oils using chemometric analysis.

The analysis of the effect of cultivar and olive leaves addition before the extraction on the different analytical values revealed significant differences (p < 0.05) in some parameters, mainly in peroxide value, phenols and tocopherol contents, and oxidative stability. Aroma profiles were also influenced by the different varieties and the addition of different amounts (0% and 3%) of olive leaves. Twenty-three compounds were characterized, representing 86.1-99.2% of the total volatiles. Chétoui cultivar has the highest amount of (E)-2-hexenal, followed by Chemlali cultivar, whereas (E)-2-hexen-1-ol was the major constituent of Zalmati and crossbreeding Chemlali by Zalmati cultivars. Sensory analysis showed that Chemlali and Chétoui Zarzis possessed a high fruity, bitter, and pungent taste, whereas the Zalmati and crossbreeding Chemlali by Zalmati had a 'green' taste among its attributes. Indeed, the taste panel found an improvement of the oil quality when an amount of olive leaves (3%) added to the olives fruits.