Mineral oil hydrocarbons
Mineral oils are comprised of various hydrocarbons. If these are aliphatic, i.e. come in the form of saturated linear and cyclic (non-aromatic) hydrocarbons with mostly 16 – 25 carbon atoms, these are referred to as “mineral oil saturated hydrocarbons” (MOSH). Aromatic, i.e. unsaturated hydrocarbons consist of mostly alkylated polycyclic compounds (usually with 1 – 4 aromatic rings) and are referred to as “mineral oil aromatic hydrocarbons" (MOAH).
How does mineral oil get into food packaging?
Mineral oil saturated hydrocarbons are predominately used as solvents. They are contained in heating oils, lubricants and motor fuels, but also in many printing inks as used for newspapers, for example. When producing cardboard boxes from recycled recovered paper, mineral oil saturated hydrocarbons get into the food packaging. It is currently not possible to eliminate a sufficient quantity of these substances during the recycling process. Mineral oils may also be found in inks and colours used for printing food packaging. Contamination from packed raw materials (e.g. printed jute bags) cannot be ruled out either. With mainly dry food with a large surface area being packed in cardboard boxes, the volatile mineral oils find their way into the food by gas phase diffusion.
What effects do mineral oils have on human health?
Mineral oil saturated hydrocarbons (MOSH) are absorbed by the body and stored in various organs. Animal testing has shown that this kind of mineral oil mixtures is deposited in the body and may cause damage to the liver and the lymph nodes. The exact composition of the mixtures in printer’s ink, especially of the fraction that contains aromatic hydrocarbons (MOAH), is not known.
There is currently no toxicological data for the evaluation and derivation of limit values for MOAH. The opinion of the Federal Institute for Risk Assessment (BfR), stating the potentially carcinogenic effect of the aromatic hydrocarbon fraction, was confirmed this year by the European Food Safety Authority (EFSA). For this reason no detectable migration of MOAH to food should be allowed to take place.
The data required for the evaluation of MOSH in the molecular weight range after migration from recycled cardboard is currently insufficient. The joint FAO/WHO Expert Committee on Food Additives (JECFA) has therefore withdrawn the temporary ADI (acceptable daily intake) this year. An ADI value specifies the amount of a substance a person can ingest each day for their entire life without needing to expect a hazard to health. The BfR has concluded a guide value for migration to foodstuffs of 12 mg/kg for MOSH with hydrocarbon chain lengths of C10 to C16. Currently a guide value for MOSH up to C20 is being discussed. There is evidence that MOSH with larger chain lengths is deposited in the human body. Migration of these substances should therefore be minimised as much as technically possible.
The European Food Safety Authority (EFSA) has estimated that we ingest between 0.03 and 0.3 mg saturated hydrocarbons (MOSH) per kilogramme of body weight with our daily food, children may ingest even more. The intake of aromatic hydrocarbons (MOAH) is estimated by the EFSA to be around 20% of the values for MOSH, i.e. between 0.005 and 0.06 mg per kilogramme of body weight. For a child weighing 10 kg this implies a daily intake of up to 3 mg MOSH and 0.6 mg MOAH.
Draft ordinances on mineral oils and printing inks
The German Federal Ministry of Food, Agriculture and Consumer Protection has presented two draft ordinances aiming at reducing the migration of mineral oil residues from recycled packagings to foodstuffs.
The most recent draft for a so-called mineral oil ordinance (22nd ordinance amending the food contact material regulation) of 24 July 2014 intends to limit the concentration of MOSH and MOAH in food contact materials that are made from recycled paper. According to this, they may only be put on the market if they do not exceed the maximum levels of 24 mg of MOSH and 6 mg of MOAH per kg of paper, paperboard or cardboard. The carbon range these concentrations refer to depends on the respective intended use. In food contact materials used for storing dry and non-greasy foods at room temperature or below they would apply to a carbon range of C16 to C25, and to a range of C16 to C35 in all other food contact materials.
Furthermore, the draft specifies that food contact materials exceeding the stated maximum levels may still be marketed if the amount transferred to the food is no more than 2 mg of MOSH and no more than 0.5 mg of MOAH per kilogramme of food. The party marketing the food contact materials must in this case provide documents that explain how these requirements are met. This may be done by: stating the conditions and results of any migration tests and calculations performed, including model calculations, describing other analyses performed, or any other methods that prove conformity. These also include documentation proving that the respective food contact material contains a functional barrier.
Mineral oils can also be transferred to food through direct printing on the packaging. To avoid this, the ministry is working on a second draft ordinance banning the use of printing inks containing mineral oils on food packagings: the so-called printing ink ordinance (21st ordinance amending the food contact material regulation).
Note: The regulations presented in the above paragraphs are drafts that currently have no official regulatory status.
Analysis of MOSH and MOAH
In the ifp laboratory the hydrocarbon fractions are separated by HPLC couple with GC. Attention should be paid to the fact that inappropriate sampling or sample containers as well as transport can lead to false-positive results. The sampling point in the product (inner or outer layers) is also important. Specific purification steps performed at ifp can eliminate analytical misinterpretations. The samples are evaluated using characterized standards. The detection limit for MOSH and MOAH is 0.15 mg/kg, respectively, the quantification limit is 0.5-0.6 mg/kg depending on the sample material.