Impact of deodorisation time and temperature on the removal of different MOAH structures: a lab-scale study on spiked coconut oil.

Abstract

Vegetable fats and oils are prone to contamination by mineral oil hydrocarbons due to the lipophilic and ubiquitous character of the latter. As the aromatic fraction of these hydrocarbons, MOAH, is associated with carcinogenicity, mutagenicity, and detrimental effects on foetal development, finding strategies to limit or reduce their contamination is highly relevant. Deodorisation (i.e. a refining step) has shown the ability to remove MOAH < C25 in vegetable fats and oils, but there is little information about the structures removed. Therefore, the present study investigated the impact of deodorisation conditions on the removal of different structures of MOAH in spiked coconut oil. An inscribed central composite design was built with time and temperature as variables (0.5-4h, 150-240 °C), while pressure (3 mbar) and steam flow (1 g water/g oil per hour) were kept constant. The analysis of MOAH in the oil was performed using a fully automated liquid chromatography coupled with two parallel comprehensive two-dimensional gas chromatography systems with flame ionisation and time-of-flight mass spectrometric detection. Response surfaces plotting the MOAH loss according to time and temperature were built for different MOAH fractions. The latter were defined based on the number of aromatic rings (>3 or ≤3) and the number of carbon atoms present (C16-C20, C20-C24, C24-C35, C35-C40). It was found that at 200 °C, compounds < C24, including weakly alkylated triaromatics, could be reduced to below the limit of quantification, while at 230 °C, it was possible to remove >60% of the C24-C35 fraction, including pentaromatics of low alkylation.