A study on the impact of harvesting operations on the mineral oil contamination of olive oils

During the 2020-21 olive oil campaign, the contribution of harvesting operations to mineral oil saturated (MOSH) and aromatic hydrocarbon (MOAH) contamination was studied. Oils extracted from hand-picked olives (15 different olive groves) generally had background MOSH (<2.7 mg/kg), and no quantifiable MOAH. In 40% of the cases, an important contamination increase was observed after harvesting operations. Except for one sample (325.8 and 111.0 mg/kg of MOSH and MOAH, respectively), other samples reached 4.3-33.7 mg/kg of MOSH and 1.1-11.3 mg/kg of MOAH. Accidental leaks of lubricants and/or contact with lubricated mechanical parts, were identified as important sources of contamination. Chromatographic traces obtained by on-line high-performance liquid chromatography (HPLC)-gas chromatography (GC)-flame ionization detection (FID) allowed for source identification. A comprehensive two-dimensional gas chromatographic platform (GC x GC) with parallel FID/MS detection was implemented for confirmation and to attempt the characterization of the contaminations. Good harvesting practices are suggested to minimize contamination risks.

Automated summary

During the 2020-21 olive oil campaign, the contribution of harvesting operations to MOSH and MOAH contamination was studied. Hand-picked olives generally had low levels of MOSH and no quantifiable MOAH. However, contamination increased significantly after harvesting operations in 40% of the cases, with accidental leaks and contact with lubricated mechanical parts identified as important sources. Source identification was done through chromatographic traces obtained by HPLC-GC-FID, and confirmation and characterization were attempted using GC x GC with parallel FID/MS detection. Good harvesting practices are recommended to minimize contamination risks.