Dosage des hydrocarbures saturés d’huile minérale (MOSH) et des hydrocarbures aromatiques d’huile minérale (MOAH) dans les huiles végétales
Lipides, Qualité, Contaminant, MOSH, MOAH
Intervention de Florence Lacoste, Responsable Département Analyse & Expertise, et Erik Becker, Institut Kirchhoff Berlin, au World Congress on Oils & Fats, le 10 février 2020 à Sydney : « Determination of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in vegetable oils ».
Contamination of vegetable oils with mineral oil hydrocarbons may come from different sources: environmental origin, crop protection, production process (lubricant leak from the machinery) or transport & storage. Several cases of contamination with mineral oil hydrocarbons were reported. In each case, the signal was characterized by gas chromatography as a huge hump of unresolved complex mixture, with thin peaks of natural odd-numbered n-alkanes.
According to the EFSA scientific opinion published in 2012, mineral oils are complex mixtures of hydrocarbons that are composed of saturated hydrocarbons (MOSH) such as linear and branched alkanes, or alkyl-substituted cycloalkanes, and may contain aromatic hydrocarbons (MOAH).
In 2019, JRC issued a guidance document covering sampling and analysis of MOSH and MOAH in food and food contact material in the frame of Recommendation (EU) 2017/84 for the monitoring of mineral oils (Bratinova & Hoekstra, 2019).
Meanwhile, two standardised methods covering the determination of mineral hydrocarbons in vegetable oils and fats were issued:
– in 2015, ISO 17780 was published for the determination of MOSH with a limit of application fixed at 50 mg/kg;
– in 2017, EN 16995 was published for the determination of MOSH and MOAH by online HPLC-GC/FID, suitable above 10 mg/kg.
The main critical steps of the analysis are linked to the fatty matrix, interferences with endogenous hydrocarbons, peak integration, and interpretation of the chromatograms and calculation of results.
Although online HPLC-GC/FID is still considered as the method of choice in routine analysis, for difficult samples and matrices, further characterisation of the MOSH/MOAH fractions need to be performed by using additional analytical techniques, e.g. GCxGC-TOF-MS.
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