Reducing polycyclic aromatic hydrocarbons (PAHs) formation in olive pomace oil using microwave pre‐heating of olive pomace

Abstract

High temperature application during drying of olive pomace before solvent extraction leads to formation of polycyclic aromatic hydrocarbons (PAHs) and their eventual presence in the oil. Therefore, the objective of this study was to investigate a mitigation possibility of PAHs in olive pomace oil. For this purpose, microwave pre‐treatment was applied to the olive pomace before drying at 200°C to final moisture content of less than 5%. Effect of pre‐drying microwave process was carried out against drying at 200°C and vacuum drying. PAH content analysis of the solvent extracted oil was completed using a HPLC method with fluorescence detection (HPLC‐FLD). The results demonstrated that the pre‐microwave application led to 75% reduction of total PAHs content in olive pomace oil. This study highlighted the possibility of an alternative innovative strategy to apply in a process to suggest a simple solution for a significant industrial problem. Practical applications: PAHs are serious problem in olive pomace oil. Removal of PAHs in olive pomace oil has a great importance because of their carcinogenic potential. Results show that PAHs are formed during drying of olive pomace at high temperature (200°C). This study reveals that microwave application was effective strategy to reduce PAHs in olive pomace oil. Therefore, drying process was modified with microwave pre‐heating application to produce high quality olive pomace oil. In this study, the effect of microwave pre‐heating application before drying to reduce PAH formation in olive pomace oil is demonstrated. The eventual reduction of total PAH concentration in olive pomace oil indicated the effectiveness of this pre‐heating application.

Further Evidence on the Removal of Polycyclic Aromatic Hydrocarbons (PAHs) During Refining of Olive Pomace Oil

“…Water and/or acid degumming are applied for soft oils depending on phosphatide type and content. In this study, water (1, 2%) and phosphoric acid (0.1, 0.2, and 0.3%) were used for the degumming of crude olive pomace oil that may contain high amount of total 15 PAHs (Np, Anp, Flr, Phe, Ant, Flu, Pyr, BaA, Chr, BbF, BkF, BaP, DahA, BghiP, and IcdP) as reported by Kiralan et al, most of which are possibly formed during air drying at high temperatures applied before solvent extraction. Crude olive pomace oil has to be refined before human consumption and refining process should also reduce PAHs content less than maximum allowable limit of 10 ppb for total of four PAHs, as indicated in EU Regulation…”

“…Contamination of vegetable oils by PAHs can occur mainly by environmental pollution of the oil bearing plants harvested from contaminated soil, water, and air . Solvents used for oil extraction and drying process of oil seeds at high temperatures might be other factors for their contamination. Crude olive pomace oil might have high amount of PAHs, depending on drying conditions of olive pomace before solvent extraction …”

A Review on the Occurrence and Analytical Determination of PAHs in Olive Oils

“…EVOO, which is extracted from olive fruits exclusively by mechanical processes without any further treatment, generally contains very low amounts of PAHs, which can be mainly traced back to environmental sources [ 45 ]. As observed in Table 2 , in all cases, except for a sample from Syria, PAH4 values were well below the EU legal limits (10 µg/kg).…”

“…OPO cannot be used directly for human consumption, undesired minor components and organoleptic properties need to be removed by refining (including degumming, neutralization, partial elimination of waxes, bleaching with activated clays, and deodorization) [ 48 ]. In OPO, high PAH levels occur despite the refining process due both to the complexity of the matrix and the high initial content of PAHs [ 45 , 49 ] ( Table 2 ). PAH contamination may occur during pomace storage [ 50 ] and the drying and solvent extraction phases [ 45 , 49 ].…”

“…In OPO, high PAH levels occur despite the refining process due both to the complexity of the matrix and the high initial content of PAHs [ 45 , 49 ] ( Table 2 ). PAH contamination may occur during pomace storage [ 50 ] and the drying and solvent extraction phases [ 45 , 49 ].…”