Olive oil enrichment in phenolic compounds during malaxation in the presence of olive leaves or olive mill wastewater extracts

Abstract

A combined study was performed to determine the effect of olive leaf aqueous extract (OLE), olive mill wastewater (OMWW) or water addition during the malaxation step on total phenolic content (TPC), antioxidant activity, virgin olive oil composition and quality parameters of olive oil. For these purposes, the Folin‐Ciocalteu assay, 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay, and HPLC‐ESI‐TOF/MS were employed. The experiments were carried out at semi‐industrial scale in a cold extraction olive oil mill using olives of Koroneiki cultivar. Olive oil produced by olive paste which was malaxed without adding water, OMWW, or OLE was employed as control. The use of OMWW and OLE allowed obtaining oils with higher significant TPC compared to that malaxed with water (146.2 and 151.8 vs. 132.8 μg Eq GAE/g oil, respectively). The antioxidant activity followed the same trend. The use of OMWW and OLE enabled an oil enrichment in oleuropein derivatives, especially in 3,4‐DHPEA‐EDA. Despite the fact that acidity and oxidation (K270 and K232 values) were higher in the aforementioned oils compared to the oil extracted with water, all values were under the European Union commission parameters for extra virgin olive oil (EVOO) denomination. However, only the oil extracted using OLE presented slightly higher fruity, bitter, and pungent positive attributes compared to the control and to the oil extracted with water, thus, making OLE a promising by‐product for improving olive oils. Practical applications: This research provides new insight for the improvement of olive oil extraction process in order to obtain high‐phenol EVOO which could be useful for the olive oil, nutraceuticals, and cosmeceuticals industries. Besides, this study could serve as a starting point for improving the olive oil production process, while reducing the impact of its by‐products. The addition of Olive mil wastewater (OMWW) and olive leaf extract during malaxation, allowed obtaining enriched oils with a higher content in total phenolics, and antioxidant activity compared to those obtained adding water. These enriched oils presentes higher quantities of oleuropein derivatives and specifically of 3,4‐DHPEA‐EDA.

The challenge of exploiting polyphenols from olive leaves: addition to foods to improve their shelf‐life and nutritional value

“…Despite the increased induction time, an increase in the oxidation parameters (peroxide value and wileyonlinelibrary.com/jsfa spectrophotometric constants), that could be presumably related to different factors, such as the improved oxygen exposure in the olive paste added with leaves during malaxation, but also the increased amount of other components, such as the pheophytin acting as pro-oxidant in light. However, Kiritsakis et al 64 evaluated the feasibility of co-malaxation of olive paste with OLE, finding an increased amount of total phenolic content (TPC) of the oils respect to the control trial, although not statistically significant. Accordingly, olive oils extracted using OLE presented the highest antioxidant activity (by means of the stable chromogenic radical 1,1 0 -diphenyl-2-picrylhydrazyl assay) compared to the control, likely thanks to the enhanced content in oleuropein aglycone derivatives, which represented approximately 12% of OLE extract total phenolic composition.…”

Composition, polyphenol bioavailability, and health benefits of aronia berry: a review

“…The use of olive mill waste water (OMWW) and olive leaf extract (OLE) during olive paste malaxation, gave enriched oils with a higher content in total phenolics, and with higher antioxidant activity. These enriched oils contain higher quantities of oleuropein derivatives and specifically of 3,4-DHPEA-EDA (Figure 3) (Caporaso et al, 2018;Kiritsakis et al, 2017b;2017c;Venturi et al, 2017).…”

The Use of Olive Leaves in Buža Olive Cultivar Oil Production: Exploring the Impact on Oil Yield and Chemical Composition

“…Virgin olive oil (VOO) is produced solely from olive fruits (Olea europaea L.) by mechanical or physical processes that include fruit crushing, olive paste malaxation, and oil extraction [1]. VOO is an important source of fat in the Mediterranean diet and is a valued product with rich nutritional properties and unique aroma and taste [2]. It is considered a functional food due to its high content of monounsaturated fatty acids and bioactive compounds, such as phenolic compounds [3].…”