Effects of reclaimed wastewater irrigation and fertigation level on olive oil composition and quality

BACKGROUND: Irrigation of olives increases fruit and oil yields. Due to scarcity of freshwater, low-quality water including recycled wastewater (RWW) is utilized in orchards. Here, effects of irrigation with RWW and of fertilization on the composition and quality of olive oil were studied. RESULTS: Long-term RWW irrigation of ‘Barnea’ and ‘Leccino’ olive had no significant negative effects on either oil composition or quality parameters, including free fatty acids (FFAs), peroxide value (PV), total phenolics content (TPC), fatty acid profiles and organoleptic characteristics. The average FFA contents for both cultivars were less than 0.8% during most of the experimental period, except the seasons 2009 and 2012–2013 for Barnea where the values were raised up to 1.4%. The measured PV levels were less than 9 and 5 mmol O₂ kg^-1 oil for Barnea and Leccino, respectively. In the last season of the experiment for each cultivar, higher TPC were observed in oils obtained from RWW irrigation with reduced fertilization (Re–) as compared to the treatments with the recommended fertilization [freshwater irrigation (Fr) and RWW irrigation (Re+) with standard dose of fertilizers], where the TPC increment exceeded 70% in Barnea and 25% in Leccino. The treatments had only minor effects on the fatty acid profile, reflected in slightly altered levels of C18:2 and C18:3 fatty acids. CONCLUSION: The use of RWW, combined with the consideration of nutrients arriving with such water to provide appropriate fertilization, was found suitable for olive irrigation to ensure optimal yields while preserving oil quality.