engleski

Effect of olive leaf addition during extraction on antioxidant content and sensorial quality of Buža cv. virgin olive oil

Buža cv. virgin olive oil (VOO) obtained from fruits in advanced ripening stage has a low level of phenolic compounds and consequently, low oxidative stability and short shelf life. Olive leaves are a natural source of antioxidants, but are usually removed from olive fruits before the processing of VOO. In this study, the strategy for the enrichment of olive oil with leaf phenolic compounds and pigments, as well as the effect of leaf addition during the VOO extraction on the sensory quality of Buža oil is examined. For that purpose, Buža cv. olive fruits, in the advanced stage of ripeness (RI = 4.04), were harvested and the fresh leaves of the same cultivar at different rates (0% - control and 1, 2.5 and 5%) were added prior to oil extraction by a laboratory scale olive mill. Phenolic composition was determined using an HPLC-DAD system, pigments were determined spectrophotometrically and sensory analysis was performed by Panel test. Total phenols did not change significantly, although changes in concentration of some individual phenols were observed. Hydroxytryrosol had the highest concentration in the oils with 5% leaf addition, while the other three phenols (vanilic acid, oleuropein – ligstroside aglycones I, II and oleuropein aglycone (isomer II)) had the highest concentrations in the oils without leaf addition. The increasing rate of leaf addition during oil extraction induced an increase in chlorophyll and carotenoid content in obtained oils. Olive leaves addition did not affect the sensory total score and all investigated olive oil samples corresponded to the extra virgin category, but difference in particular sensory characteristics with increasing of olive leaves addition rate were observed: slightly higher intensity of olive fruitiness, aromatic herbs as well as intensity of astringency. Obtained results indicate that leaf addition up to 5% has no negative influence on Buža oil sensory characteristics, as well as on the content of total phenolic compounds, but increases oil pigment content. Further study, which investigates the oxidative stability and shelf life of Buža olive oil produced by addition of olive leaves, is needed. Acknowledgement: The work has been supported in part by the „Young researchers’ career development project – training of doctoral students“ (DOK-2018-01-4693) funded by the Croatian Science Foundation and the European Union from the European Social Fund.

Olive oil ; Olive leaf addition ; Phenolic compounds ; Pigments ; Sensory quality

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