Impact of agro-industrial factors on phenolic content antioxidant capacity of Lebanese olive mill waste water

Abstract

Background: Olive oil is a vital component in the Lebanese diet and Lebanon is known for its contribution to the global production of olive oil. During the process of olive oil extraction, a brownish black effluent is also produced called Olive mill waste water (OMWW). OMWW is disposed into the environment causing serious polluting problems harming the aquatic and terrestrial organisms and reaching the underground water as well. OMWW contains considerable amount of phenolic compounds with antioxidant properties. In Lebanon, no study did extract and assess the levels of these phenolic compounds from OMWW and the effect of different agro industrial factors on them and on their antiradical scavenging capacity (ASC). Objectives: This study aimed at finding the most appropriate method to extract these phenolic compounds from OMWW, and at identifying the agro-industrial factors that affect them and their ASC. Methods: OMWW samples (n= 44) were collected in 2016 in collaboration with the Lebanon Industry Value Chain Development (LIVCD) project and the Lebanese Agricultural Research Institute (LARI) Hasbaya and Tal Amara stations, from two different regions (Zgharta/Koura in the North and Jezzine/Hasbayya in the South), and from three different processing systems: press, 3-phase and sinolea. In addition, samples were obtained in triplicate at three different harvesting times (from three different farmers at each harvesting time). Liquid-liquid extraction using ethyl acetate, Folin-Ciocalteu reagent, and 2, 2-diphenyl-l -pircylhydrazyl (DPP H) were used for the extraction of the total phenolic content (TPC), their quantification, and the assessment of their ASC respectively. Results: This study showed that the most efficient way to extracting the phenolic compounds from the OMWW was by Liquid-liquid extraction method. The mean TPC was 789.7 +222.4 mg GAE.kg-1 of OMWW ranging between 125.3 mg GAE.kg-1 and 2018.0+226 mg GAE.kg-1 of OMWW. As for the ASC, measured in terms of mg of Tocopherol Equivalence (TE) per Kg of OMWW, the mean value was 987.6 ± 387 mg TE. Kg-I ranging between 91.9 ± 0. I mg TE.kg-l and 3328.5 ± 919.0 mg TE.Kg-l. A strong and positive correlation between the TPC and the ASC was observed (r — 0.784). The three factors considered: the geographical origin of the olive fruits, the harvesting time and the oil processing system are factors of primary importance on the TPC and ASC of OMWW. The two-way interaction geographical origin* harvesting time presented a significant effect (p < 0.05). As per each factor alone, only the geographical origin revealed a significant effect on ASC (p = 0.001) with higher ASC in Akkar (1880.07 TE) compared to Hasbaya (682.05 TE). ANOVA results showed that the harvesting time is the main contributor for the total variance of TPC (14.69%). These results indicate that, whatever the geographical origin, there is always difference and variation of these two parameters across the three-harvesting time. However, the geographical origin figures as the main contributor for total variance of ASC (20.34%). Conclusion: The presence of phenolic compounds in the OMWW with potent ASC can be used in food industries and many pharmaceutical industries. Further studies can be done in order to confirm our results and to assess other factors that might affect the level of TPC and their antioxidant capacity such as water quantities used for olive tree irrigation, type of olive cultivar and olive transportation and storage.