Entry #: 38
Date: 27 February 2018
Section: Phenolic extracts
Topic: Phenolic extracts and anti-microbial effects
Type: Original paper
OliveNetTM Journal Club
Expert review of literature related to olives and olive oil
D. Elizabeth McCord, Nancy B. Ray and Tom C. Karagiannis
Enrichment of phenolic compounds from olive mill wastewater and in vitro evaluation of their antimicrobial activities
Abu-Lafi et al
Citation / Year
(1) / 2017
Phenolic extracts, olive mill wastewater, hydroxytyrosol, tyrosol, antibacterial, antifungal
Production of olive oil results in the accumulation of huge amounts of olive mill wastewater. This wastewater contains phytotoxins representing an important environmental issue, and presents difficulties associated with storage or disposal (2, 3). Given the high levels of phenolic compounds in olive mill wastewater, there is considerable interest in utilising this material as a starting point for enriching or even isolating pure bioactive compounds (4, 5). For example, phenolics compounds could have important applications in the food industry, supplements, cosmetics, pharmaceutical industries (5, 6). Therefore, cost-effective methodologies for enriching or isolating bioactive compounds from olive mill wastewater is an important research direction. As a proof-of-principle, in this work, ethyl acetate was utilised as solvent for preparing polyphenolic extracts from 20 litres of wastewater collected from an olive mill.
Key points and implications
The ethyl acetate extraction process resulted in polyphenolic extracts with an approximately 1% (wt/wt) yield. The extracts were shown to contain the key bioactive olive phenolics, hydroxytyrosol and tyrosol; oleuropein was not detected in the extracts. Similarly, a significant flavonoid content was detected. The antioxidant activity of the extracts was monitored using the ferric and cupric reducing antioxidant assays and well-established in vitro assays were utilised to determine free radical scavenging activity. Importantly, bioactive properties of the extract was highlighted using these antioxidant and free radical scavenging assays. The findings also indicated the extracts possessed and antibacterial activity against Staphylococcus aureus (gram positive), and Escherichia coli (gram negative). Similarly, the extract was effective against Candida albicans and Aspergillus niger highlighting antifungal properties. Given these properties, extracts were introduced into olive oil (at 0.5 and 1%), to improve the antioxidant content and preservation of the olive oil, is indicated by enhanced stability, oil acidity, and peroxide value. Overall, this work represents a key research direction with respect to an important environmental issue arising from the production of olive oil. The possibility of cost-effective enrichment of bioactive compounds from essentially a waste product is anticipated intensely pursued in future research efforts.
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