Recycled fibre-based materials are a major source of hydrocarbon mineral oils in foods. Omya explains how it is responding to a call from the German Government to solve this contamination problem.
In 2012, German consumer foundation Stiftung Warentest published data showing that hydrocarbons were present in the chocolates in children's advent calendars. The recycled cardboard packaging was identified as the source of the leakage, and the likely result will be a blanket ban on the use of mineral oils in that country.
Mineral oils are a colourless, odourless mixture of higher alkanes, usually derived from petroleum. The most sophisticated ('cleanest') products create the least apparent contamination; the purest class of crude oils are white mineral oils, which contain only saturated and cyclic alkenes, with no aromatic or unsaturated components.
Vegetable oils may be safely consumed, but mineral oil-derived substances can accumulate in human tissue. Saturated hydrocarbons agglomerating in liver tissue, for example, are a health risk, while aromatic hydrocarbons are potentially carcinogenic and may have an estrogenic impact. The main source of such substances in foods originates from primary packaging materials, which is where recycled fibres come in.
The 23 million or so tons of newspaper that is printed every year uses approximately 1.2g/m² of printing ink, up to 30% of which is mineral oil, and 120,000t of that then ends up in recycled fibres.
Mineral oils can also originate from natural sources for example, from the incomplete burning of hydrocarbons; batching oils from sisal and jute bags; lubricants used in the paper, board, food production, or from the packaging process. Calling for mineral-oil-free printing inks is one way to lower the contamination level, but does not solve the problem entirely because:
Online liquid chromatography - gas chromatography - flame ionisation detector (LC-GC-FID) is a reproducible method for detecting mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH). Because the chromatograms also display polyolefin oligomeric saturated hydrocarbons (POSH), polyalpha olefine (PAO) and white mineral oils (MOSH), an accredited and experienced laboratory is vital for reliable results in order to guarantee a correct interpretation of the 'hump' of the chromatography.
In the EU, the maximum levels of mineral oils in food stuffs are regulated for the fractions of C10 up to C20 for MOSH only.
Thanks to work by the EU Recommendations Commission's Vytenis Andriukaitis in January 2017 on monitoring of mineral oil hydrocarbons in food and in materials and articles intended for food contact, a legal clarification and binding definition can be expected in 2019.
PLA, PET or PA are the preferred options for the polymer film-based packaging industry. These are known to have excellent barrier properties against MOH, but have recyclability issues if used as coextruded or laminated part of a non-separable multimaterial combination that cannot be recycled with existing technology.
Besides controlling the plantation, harvesting, transportation and handling of raw materials, and the production and/or packaging process of food, smart selection of the means of packaging materials is essential. The gaseous state of the mineral oils means that changing the primary packaging material from fibre to polymer is not necessarily feasible.
The barrier performance of polymers such as PC, PS and - most importantly - PE and PP against MOH is certainly insufficient. With PE and PP as the two most important films on packaging, no significant barrier can be achieved. For products with very short shelf lives, high-gauge PP films can be adequate, whereas long-term storage requires functional barriers, which can only be guaranteed with protective layers.
PET, PVdC, PA or aluminium are typically co-extruded or laminated to the primary substrate. Others such as PLA, xylane, cellophane, PVOH, EVOH or starch have proven performance, but are disadvantageous in terms of cost, applicability and mechanical stability.
Acrylic-based materials - like a blend of speciality pigments with a dispersion based on acrylic ester and methacrylic ester - are currently the most convenient option. Extomine BM from Omya is a water-based, ready-to-use mineral oil barrier that can be coated, printed or sprayed.
More than 52% solids guarantee easy applicability and swift drying, while high machine speeds can be achieved, thanks to minimised blocking. Omya is convinced that Extomine BM is one of the smartest ways to guarantee polmyer film-based safe food packaging, coated, printed or sprayed.