Activated carbon bleaching for MOAH mitigation in palm oil: a multi-parameter laboratory-scale study using HPLC/GC × GC-FID.

Abstract

Mineral oil hydrocarbons (MOH) are lipophilic food contaminants that can be present in edible oils. Mineral oil aromatic hydrocarbons (MOAH) are a sub-fraction of MOH and are of particular concern for the European Food Safety Authority (EFSA), as MOAH containing three or more aromatic rings are considered potentially genotoxic. Several studies have shown that certain steps in vegetable oil refining can reduce MOH levels. Deodorisation, in particular, has been reported to significantly decrease overall MOH concentrations. More recently, bleaching with activated carbon (AC) has also been identified as a possible mitigation tool for MOAH. However, no quantitative study has been conducted yet on real edible oil matrices examining the effect of bleaching treatments on MOAH subclasses. The objective of this study was therefore to investigate the effect in spiked palm oil of AC bleaching on the mitigation of MOAH sub-classes (i.e. C-fraction and number of aromatic rings), using HPLC/GC × GC-FID. Two palm oils (preliminary differently treated) were tested with two types of AC. The mitigation effect was evaluated using a Doehlert experimental design combined with response surface methodology, assessing different temperatures (60-80-100 °C) and AC dosages (0.3-0.68-1.05-1.43-1.8%, w/w). Pressure (50 mbar absolute) and contact time (30 min) were kept constant. The results demonstrated that MOAH with three or more aromatic rings can be significantly mitigated by AC bleaching, whereas the adsorption of 1-2 rings MOAH occurred to a much lower extent. In addition to the aromatic ring number, the degree of alkylation influenced adsorption behaviour, with more highly alkylated MOAH showing lower affinity for AC. Among the investigated factors, AC concentration was the most influential parameter: increasing AC dosage led to greater MOAH reduction. Temperature also affected MOAH mitigation in an AC-type-dependent manner. Both AC types resulted in comparable maximal MOAH reductions in both oils, i.e. around 25-30%.