`Irrigating with Wastewater Found Not to Affect EVOO Quality - Olive Oil Times
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Irrigating with Wastewater Found Not to Affect EVOO Quality

By Sukhsatej Batra
Feb. 29, 2016 09:12 UTC

Water is fast becom­ing a scarce com­mod­ity with an esti­mated 40 per­cent global water deficit expected by 2030, accord­ing to the 2015 World Water Development Report. Low water sup­plies would espe­cially affect agri­cul­ture and could pos­si­bly lead to a decrease in land used for food cul­ti­va­tion.

One area of con­cern is the Mediterranean region, which uses as much as 64 per­cent of its water for agri­cul­tural pur­poses, accord­ing to a 2010 paper, The Water Issue in the Mediterranean, by Eugenia Ferragina, pub­lished by the European Institute of the Mediterranean (IEMed) and the European Union Institute for Security Studies (EUISS).

Although Tunisia usu­ally stands as the fourth-largest pro­ducer of olive oil, it is an arid Mediterranean coun­try with lim­ited water resources. Concern over its depen­dency on con­ven­tional irri­ga­tion meth­ods and the fore­cast of declin­ing water sup­ply prompted Tunisian researchers to inves­ti­gate qual­ity of olive oil with use of uncon­ven­tional water sources for grow­ing olive trees.

The results of the study were pub­lished on February 17, 2016 in the Journal of Agricultural and Food Chemistry.

The exper­i­men­tal orchard with olive trees of the Chemlali cul­ti­var in the city of Sfax in Tunisia was irri­gated with two major sources of waste­water – treated waste­water from domes­tic and indus­trial sources; and olive mill waste­water pro­duced dur­ing olive oil extrac­tion from a mill also located in the city of Sfax.

For the study, inves­ti­ga­tors irri­gated olive trees using the con­ven­tional water source as a con­trol; and olive mill waste­water at either 50, 100 or 200 m³/ha; and treated waste­water in the exper­i­men­tal group.

The researchers found that the polyphe­nol con­tent of extra vir­gin olive oil from trees irri­gated with olive waste­water and treated waste­water was sig­nif­i­cantly higher than polyphe­nol con­tent of EVOO from the con­trol group. The polyphe­nol con­tent was espe­cially higher in EVOO from trees irri­gated with olive mill waste­water at 50 and 100 m³/ha.

Concentration of α‑tocopherol in the extra vir­gin olive oil was high­est from trees irri­gated with 50 m³/ha of olive mill waste­water, but decreased inversely with increase in trees irri­gated with olive mill waste­water at 100 or 200 m³/ha. α‑tocopherol con­tent was low­est in extra vir­gin olive oil pro­duced from trees irri­gated with treated waste­water.

Treated waste­water, how­ever, increased the linoleic con­tent but decreased the oleic acid con­tent of the extra vir­gin olive oil. Overall, the acidic pro­file analy­sis showed that extra vir­gin olive oil from trees irri­gated with olive mill waste­water had a bet­ter fatty acid com­po­si­tion than oil from trees irri­gated with treated waste­water.

The researchers point out that regard­less of the water source used to irri­gate olive trees, all olive oil pro­duced was extra vir­gin olive oil. The study con­cludes that irri­gat­ing olive trees with olive mill waste­water or treated waste­water in place of con­ven­tional water sources could be an effec­tive way of pre­serv­ing water with­out affect­ing qual­ity of extra vir­gin olive oil.

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