Effect of olive leaf extract rich in oleuropein on the quality of virgin olive oil

Abstract

Effect of olive leaf extract rich in oleuropein on the quality of virgin olive oil was investigated. After extracting the dried and ground olive leaves with the assistance of homogenizer, the dried extract was partially dissolved into the oil to increase the oxidative stability of the oil. A face central composite design through response surface methodology was used to investigate the effects of enrichment conditions (extract content, time and mixing speed) on the responses, total phenolic content and oleuropein concentration of the enriched olive oil. Furthermore, antioxidant activity of the oil was determined by 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt method. Additionally, oxidative stability of the enriched oil was assessed by the Rancimat method. Total carotenoid content, peroxide value, α-tocopherol and chlorophyll were also measured, respectively. Addition of 0.15% natural antioxidant increased the stability of the oil (≈46%). The antioxidant capacity of the enriched oil was almost 2.5 times higher than that of the untreated oil. Furthermore, olive leaf extract improved the quality of the virgin olive oil with respect to tocopherol, carotenoid and chlorophyll contents and peroxide value, respectively. The leaf sampling was also performed both in the autumn and summer to evaluate the possible seasonal effects on phenolic profile in order to be careful for selecting the proper harvesting time to apply the extract into the oil.

Optimization of Bioactive Substances in the Wastes of Some Selective Mediterranean Crops

“…The model proposed for grapefruit peel extraction had a non-significant lack of fit value (p > 0.05), meaning that the model is in good agreement with the experimental output. However, the remaining models had significant values for lack of fit, showing similarity with the other reports [33][34][35][36][37][38]. Kittisuban et al declared that lack of fit with a significant value might be acceptable if there are lots of data in the relevant process system [37].…”

Development and validation of an HPLC‐DAD method for determination of oleuropein and other bioactive compounds in olive leaf by‐products

“…The ideal situation would be that these leaves could be processed in the same place where they are generated, thus transforming waste to a by‐product in the oil mill industry. Until now, only the use of the olive leaf in the oil mills has been investigated from the point of view of increasing the added value of olive oil 28, 29 . One of the main reasons why the olive leaves are not used by the oil mills could be the analytical techniques used for the oleuropein quantification, such as chromatography equipment, which is not commonly found in traditional mills.…”

Synergistic effect of 3,4-dihydroxyphenylglycol with hydroxytyrosol and α-tocopherol on the Rancimat oxidative stability of vegetable oils

“…The activity of Olivefen® is higher than that reported for olive leaf extract or olive waste cake extract. 1500 ppm of olive leaf extract, rich in oleuropein, increased the olive oil stability up to 46% (Sahin, Sayım, & Bilgin, 2017), a value reached by the extract at lower concentrations (50-100 ppm). 100 and 200 ppm of olive waste cake extract, rich in HT, improved the sunflower oil stability up to 32 and 56% respectively, (Abd-ElGhany, Ammar, & Hegazy, 2010) versus the 60 and 78% using 100 and 250 ppm of Olivefen®.…”