Institut Kirchhoff Berlin GmbH

Determining mineral oil hydrocarbons in foodstuffs and packaging using HPLC-GC-FID

Date: November 2019

Background

Mineral oil hydrocarbons (MOH) are distillation products of crude oil or coal tar. They contain straight and branched aliphatic and cycloaliphatic (Mineral Oil Saturated Hydrocarbons, MOSH) as well as alkylated, partially hydrogenated aromatic hydrocarbons (Mineral Oil Aromatic Hydrocarbons, MOAH). Heterocycles may also be present. MOHs range from volatile and readily degradable hydrocarbons to poorly soluble, poorly volatile and poorly degradable high-molecular compounds from lubricating greases and oils. MOH from printing inks and recycled cartons are able to migrate into packaged food in high quantities. However, MOH in different compositions can also enter food through many other pathways. Some examples are: Impurities with "Batching Oil" from jute bags (hazelnuts, rice, cocoa beans), release agents in bakery products, paraffin oil for fining rice and as dust binder as well as hydraulic oils from dosing systems (food industry).

Toxicological classification

For a comprehensive health assessment a sufficient characterisation of the composition of the mineral oil mixtures is currently lacking. It is therefore not yet possible for the BfR to carry out a complete risk assessment. Irrespective of the risk assessment, however, these contaminations in foodstuffs are in principle undesirable.
Paraffins are one of the quantitatively most significant contaminations in the human body. Current studies show accumulation in various organs in the molecular weight range from about n-C20 to n-C46. Saturated hydrocarbons are not carcinogenic, but may act as tumour promoters and disturb the fat metabolism in high doses. Aromatic hydrocarbons are potentially genotoxic and carcinogenic (Opinion on human food exposure to 'mineral oil hydrocarbons', European Food Safety Authority (EFSA), June 2012). With regard to mineral oil mixtures with a high aromatic content (MOAH), intake should be completely avoided according to the BfR, as it cannot be excluded that carcinogenic aromatic compounds are present in the MOAH fraction.
Estimates suggest that daily dietary intake is between 0.03 and 0.3 mg saturated hydrocarbons (MOSH) per kilogram of body weight, and may be higher in children (EFSA, 2012). EFSA estimates that the intake of aromatic hydrocarbons (MOAH) is between 0.006 and 0.06 mg per kilogram of body weight. For a child weighing 10 kg, this means a daily intake of up to 3 mg MOSH and 0.6 mg MOAH.

Legal classification

The temporary ADI for Class II and Class III mineral oils of 0.01 mg/kg body weight was withdrawn in June 2012 at the JECFA Seventy-sixth meeting (Fifty-ninth report of the Joint FAO/WHO Expert Committee on Food Additives, WHO Technical Report Series 913(2002)).

Since April 2011 there has been a temporary migration limit for aromatic-free mineral oils (i.e. MOSH, used as a formulation agent for paper production) in the molecular weight range from n‑C10 to n-C16 of 12 mg/kg set by the BfR. For the fraction from n-C17 to n-C20 a migration value of 4 mg/kg food for saturated hydrocarbons was established in November 2012, also by the BfR (BfR recommendation XXXVI).

The 4th draft of the 22nd Ordinance to Amend the Commodity Ordinance (Mineral Oil Ordinance) of 07.03.2017 provides for maximum quantities for the transition from MOAH to food contact materials made of paper, cardboard or paperboard which have been manufactured using waste paper. According to this, food contact materials and articles may only be placed on the market if the maximum quantity of 0.5 mg/kg of food is complied with for the transition from MOAH (possibly through the use of a functional barrier). Up to this level, a transition is considered not to have taken place and a functional barrier is considered suitable.

Furthermore, the GMP Regulation (EC) No. 2023/2006 stipulates that every manufacturer must ensure that "materials and articles intended to come into contact with foodstuffs [...] are appropriate for their intended use without endangering human health".

Last but not least, the Contaminants Regulation (EC) No. 1881/2006 demands that for "contaminants which are to be classified as genotoxic carcinogens [...], the maximum levels shall be as low as reasonably achievable (ALARA)". The ALARA principle therefore also applies to MOAH.

Analytics

The investigation of the MOH is based on the international DIN EN 16995:2017 "Determination of saturated mineral oil hydrocarbons (MOSH) and aromatic mineral oil hydrocarbons (MOAH) with online HPLC-GC-FID" as well as on the compendium of the Federal Institute for Risk Assessment (BfR) and the Cantonal Laboratory Zurich (KLZH) for the measurement of MKW in food and packaging materials. DIN SPEC 5010:2018-05 is the publicly available specification for the investigation of migration from paper, cardboard and paperboard with Tenax® as adsorbent. This method can be used to estimate the migration potential of food contact materials.

The MOH are extracted from the sample with an organic solvent. Complex samples, e.g. tea, high-fat foods such as chocolate or fats/oils, are additionally purified before measurement using various auxiliary techniques (e.g. with activated aluminium oxide or an epoxidation step). The MOH are then determined using online HPLC-GC/FID. The normal phase HPLC retains interfering lipids and separates the MOSH fraction from the MOAH fraction. The respective fraction (MOSH/MOAH) is then detected by FID. Quantification is performed using the internal standards added prior to extraction.

Fig.1: HPLC-GC-FID chromatograms of MOSH and MOAH in an sunflower oil and a peanut oil
Fig.1: HPLC-GC-FID chromatograms of MOSH and MOAH in an sunflower oil and a peanut oil

A further characterization of the samples is carried out by means of GCxGC-TOF-MS if necessary as recommended by the JRC guidance. By coupling two-dimensional gas chromatography with a mass spectrometer, subgroups can be characterized, false positive results can be avoided and marker substances for the origin of MOH can be identified.

Fig.2: GCxGC-TOF-MS contour plot of a MOH; in addition to the respective subgroups of the MOSH and MOAH fraction, typical markers for the fossil origin (e.g. hopanes and steranes) can be identified.
Fig.2: GCxGC-TOF-MS contour plot of a MOH; in addition to the respective subgroups of the MOSH and MOAH fraction,
typical markers for the fossil origin (e.g. hopanes and steranes) can be identified.

Results

At the Kirchhoff Institute in Berlin, samples of various food matrices are analysed, including many packaging materials. For different matrices, stage controls and projects to minimize MOSH and MOAH were supported with our expertise. In packaged foods up to 60 mg/kg mineral oil hydrocarbons were determined and in many foods a basic contamination with mineral oil hydrocarbons could be determined. In general, however, the trend for MOSH and MOAH levels in foodstuffs is decreasing. The sources of contamination with mineral oil hydrocarbons are often multifactorial (e.g. raw materials, production process, transport and packaging).

The successful participation in interlaboratory comparisons of different matrices (DRRR), cooperation in method interlaboratory comparisons (e.g. ISO 17780, CEN/TC 275 N 1069, Proof ACS), in §64 working groups as well as the performance of comparative laboratory tests are only one component of the quality assurance of the results in our company.

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