Institut Kirchhoff Berlin GmbH

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

Date: March 2016

Background

Mineral oil hydrocarbons (MOH) are distillation products from mineral oil or coal tar. They contain straight and branched aliphatic and cycloaliphatic (mineral oil saturated hydrocarbons, MOSH) and aromatic hydrocarbons, which generally contain 1–5 aromatic rings (mineral oil aromatic hydrocarbons, MOAH). They can also contain heterocyclic compounds. The range of MOHs spans volatile and easily degradable hydrocarbons right up to poorly soluble, low-volatility and persistent high molecular compounds of grease and oils. Mineral oils in printing inks and recycled cardboard can migrate into packaged foodstuffs at high rates. That being said, mineral oils of various structures can also enter foodstuffs in many other ways. Some examples are: Contamination with ‘batching oil’ from jute bags (hazelnuts, rice, cocoa beans), mineral mould oils in the case of baked goods, paraffin oil for fining rice and also as dust binders or hydraulic oil from dosing systems (food industry).

Analysis

The analysis of mineral oil hydrocarbons (MOH) occurs on the basis of the soon-to-be-released international DIN EN method (planned document number: DIN EN 00275247 ‘Determination of mineral oil in vegetable oils and foodstuffs on basis of vegetable oils’ as well as on the compendium of the German Federal Institute for Risk Assessment (BfR) and Cantonal Laboratory Zurich for measuring MOH in foodstuffs and packaging materials.

The MOHs are extracted from the sample using an organic solvent. Complex samples, for example tea, fatty foods such as chocolate or fats and oils are purified using various auxiliary technologies before measurements are taken. (For example, with activated aluminium oxide, epoxidation stage). Finally, the MOHs are determined using online HPLC-GC/FID. The normal-phase HPLC holds back damaging lipids, and separates the MOSH from the MOAH fractions. The respective part (MOSH/MOAH) is then detected using FID. Quantification is on the basis of the internal standard applied before extraction.

Eine weitere Charakterisierung der Proben wird im Bedarfsfall mittels GCxGC-TOF-MS durchgeführt. Durch die Kopplung von zweidimensionaler Gaschromatographie mit einem Massenspektrometer können, Subgruppen charakterisiert, falsch positive Ergebnisse vermieden und Markersubstanzen für den Ursprung der MOH identifiziert werden.

Abb.2: GCxGC-TOF-MS Konturplot eines MOH; neben den jeweiligen MOSH- und MOAH-Gruppen sind typische Marker für die fossile Herkunft (z.B. Hopane und Sterane) erkennbar
Abb.2: GCxGC-TOF-MS Konturplot eines MOH; neben den jeweiligen MOSH- und MOAH-Gruppen sind typische Marker für die fossile Herkunft (z.B. Hopane und Sterane) erkennbar

At the moment, there lacks a sufficient classification of the composition of the mineral oil mixtures for carrying out a health analysis. Up until now, it has therefore not been possible for the BfR to carry out a complete risk assessment. But irrespective of the risk assessment, these contaminations in foodstuffs are most definitely unwanted. 

Paraffins represent one of the quantitatively most important contaminations in the human body. Current research shows accumulations in various organs in molecular weights of about n-C20 to n-C46. Saturated hydrocarbons are not carcinogenic, although in higher doses could possibly be tumor promoters. Aromatic hydrocarbons are potentially genotoxic and carcinogenic (Report on foodstuff-based exposure of humans to mineral oil hydrocarbons, European Food Safety Authority (EFSA), June 2012). According to the BfR, the ingestion of mineral oil mixtures with a high aromatic component (MOAH), should be entirely avoided, as it cannot be ruled out that aromatic compounds contained in the MOAH fraction could cause cancer.

According to estimations, between 0.03 and 0.3 mg of saturated hydrocarbons (MOAH) are absorbed per kilogramme of body weight. In children, this figure could be even higher (EFSA, 2012). According to estimates by the EFSA, the quantities of aromatic hydrocarbons (MOAH) absorbed could be between 0.0006 and 0.06 per kilogramme 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.

Toxicological classification

At the moment, there lacks a sufficient classification of the composition of the mineral oil mixtures for carrying out a health analysis. Up until now, it has therefore not been possible for the BfR to carry out a complete risk assessment. But irrespective of the risk assessment, these contaminations in foodstuffs are most definitely unwanted. 

Paraffins represent one of the quantitatively most important contaminations in the human body. Current research shows accumulations in various organs in molecular weights of about n-C20 to n-C46. Saturated hydrocarbons are not carcinogenic, although in higher doses could possibly be tumor promoters. Aromatic hydrocarbons are potentially genotoxic and carcinogenic (Report on foodstuff-based exposure of humans to mineral oil hydrocarbons, European Food Safety Authority (EFSA), June 2012). According to the BfR, the ingestion of mineral oil mixtures with a high aromatic component (MOAH), should be entirely avoided, as it cannot be ruled out that aromatic compounds contained in the MOAH fraction could cause cancer.

According to estimations, between 0.03 and 0.3 mg of saturated hydrocarbons (MOAH) are absorbed per kilogramme of body weight. In children, this figure could be even higher (EFSA, 2012). According to estimates by the EFSA, the quantities of aromatic hydrocarbons (MOAH) absorbed could be between 0.0006 and 0.06 per kilogramme 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 mineral oils of classes II and III, 0.01 mg/kg body weight, was retracted at the 76th JECFA meeting (59th report of the Joint FAO/WHO Expert Committee on Food Additives, WHO Technical Report Series 913 (2002).

Since April 2011, the BfR’s determined temporary migration threshold for aromatic-free mineral oils (MOSH, used as formulation agents for paper manufacture) in the molecular weight range of C10-C16 for 12 mg/kg has been in place. For fraction C17-C20, in November 2012 the BfR also set a migration value of 4 mg/kg of food for saturated hydrocarbons (BfR recommendation XXXVI).

The third draft of the 22nd Ordinance on Changing the Consumer Goods Ordinance (Mineral Oil Ordinance) of 27 July 2014 proposes maximum quantities of paper, paperboard or cardboard manufactured using recycled paper. The following maximum quantities were proposed:

MOSH (saturated hydrocarbons): 

C16-C25 (dry non-fatty foods) 24 mg/kg

C16-C35 (rest) 24 mg/kg

MOAH (aromatic hydrocarbons):

C16-C25 (dry non-fatty foods) 6 mg/kg

C16-C35 (rest) 6 mg/kg

If these values are not adhered to, the utensil can still however be used provided that migration limits into the foodstuff of no more than 2 mg/kg MOSH and 0.5 mg/kg MOAH are not exceeded.

Results

At the Institut Kirchhoff Berlin, more than 10,000 samples of various foodstuff matrices have been examined, of which about 650 samples were of packaging material.  Up to 60 mg/kg mineral oil hydrocarbons were detected in packaged foods. In many foodstuffs, background levels of mineral oil hydrocarbons were determined.

The sources of contamination by mineral oil hydrocarbons often span several factors (eg raw materials, manufacturing process, transport, packaging). 

Successful participation in round robin tests of various matrices, involvement in method round robin tests (eg ISO 17780, CEN/TC 275 N 1069), as well as the implementation of interlaboratory studies form just one component of quality assurance of results in our company.

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