Abstract
Olive processing wastewaters (OPW), namely olive mill wastewater (OMW) and table-olive wastewaters (TOW) were evaluated for their antibacterial activity against five Gram-positive and two Gram-negative bacteria using the standard disc diffusion and thin layer chromatography (TLC)-bioautography assays. Disc diffusion screening and bioautography of OMW were compared to the phenolic extracts of table-olive brines. Positive activity against S. aureus was demonstrated. The optimization of chromatographic separation revealed that hexane/acetone in the ratio of 4:6 was the most effective for phenolic compounds separation. A HPLC-MS analysis was performed showing that only two compounds, hydroxytyrosol and tyrosol, were the predominant phenolic compounds in all OPW. The phenolic extract of OMW generated by a semi-modern process showed the highest free radical-scavenging activity (DPPH assay) compared to the other phenolic extracts. It is apparent from the present study that OPW are a rich source of antioxidants suitable for use in food, cosmetic or pharmaceutical applications.
Highlights
Olive fruits are used in the agro-industry mainly for the preparation of table olives and oil extraction
As part of a comprehensive study of the nature and functionality of Olive processing wastewaters (OPW) phenolic extracts, we investigated the antioxidant and antibacterial activity of olive mill wastewater (OMW) samples generated by two different olive oil processing techniques, and table-olive wastewaters (TOW) samples issued from brines of table olives with different stages of maturity
In a previous work, we have found that the antioxidant capacity of different OMW extracts was directly correlated to the percentage of free hydroxytyrosol and their antioxidant activity was found to be the result of their phenolic profile rather than their phenolic concentration [19]
Summary
Olive fruits are used in the agro-industry mainly for the preparation of table olives and oil extraction. The olive oil extraction generates an effluent formed by the combination of the water content of the olive fruit with the water generated from the washing and processing of the olives. This effluent is commonly known as olive mill wastewater (OMW). This effluent is one of the most environmentally concerning food processing effluents in the Mediterranean countries due to its phytotoxicity [1]. The main olive oil extraction method used in many Mediterranean countries is the continuous centrifugation system known as three-phase system [2]
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