How can we prevent the occurrence of MOSH and MOAH in olive oil? Risks, regulations, and prevention.

Effects of oil contamination by mineral oil hydrocarbons (MOH).

Some European Union countries have pulled or even gotten rid of batches of olive oil contaminated with hydrocarbons, but why is this such a big concern? How can it be prevented?

This could pose a problem for the industry and result in a loss of status for this product in a context where it's crucial to fight for high-quality oil and fair prices.

In a society that's increasingly demanding about the quality of its food and more thorough with the quality controls of its food products, olive oil is no exception. It's within these quality controls that numerous contaminations of olive oil batches with hydrocarbons have been discovered, with two types of hydrocarbons – MOSH and MOAH – being particularly concerning.

What are MOSH and MOAH?

MOSH (Mineral Oil Saturated Hydrocarbons)

MOSH are saturated hydrocarbons derived from mineral oils, which in turn come from the distillation of petroleum. They consist of molecules made up only of carbon and hydrogen atoms linked by single bonds. They can appear as either linear or branched chains (paraffins) or as saturated cyclic structures (naphthenes). Their presence in olive oil can be due to contamination during the harvesting or production process.

MOAH (Mineral Oil Aromatic Hydrocarbons)

MOAH are aromatic hydrocarbons from mineral oils, also derived from petroleum. However, unlike MOSH, they contain benzene rings in their chemical structure. These compounds are particularly concerning because they can be genotoxic and carcinogenic, posing a significant health risk when present in foods such as olive oil.

Do they pose a health risk?

Currently, dietary exposure to MOSH is not considered a health risk, but its long-term effects require further research. On the other hand, MOAH can have more toxic effects due to their aromatic structure. They share a similar toxicity profile with their parent PAHs (polycyclic aromatic hydrocarbons) of the same ring size, which are recognized as genotoxic and carcinogenic compounds.

Current Legislation on MOSH and MOAH

Toward the end of 2023, the European Commission's Directorate-General for Health and Food Safety (DG SANTE) set the permissible limit for MOAH at 2 mg/kg for most vegetable oils, including olive oils. This limit is expected to go into effect on January 1, 2026, except for pomace olive oil, which is initially allowed a higher limit of 10 mg/kg. This higher limit is planned to be gradually reduced to 2 mg/kg by 2030.

Regarding MOSH, there is ongoing discussion about establishing indicative levels of MOSH (15 mg/kg for oils and vegetable fats) which, if exceeded, would require food operators to investigate the source of contamination and implement mitigation measures.

Health Consequences

Let's start with the less harmful substances, such as MOSH, which accumulate in the liver, spleen, and lymph nodes. Numerous studies suggest that they can cause inflammation in these organs and, over a long period, may impact fat metabolism.

However, the more concerning substances are MOAH, as they specifically contain three carcinogenic compounds, which are:

- Polycyclic aromatic hydrocarbons (PAHs). An example is benzo[a]pyrene, which binds to DNA, inducing genetic mutations and increasing the risk of cancer.

- Genotoxic compounds. These substances disrupt DNA replication, thereby damaging the genetic material in cells.

- Potential endocrine disruptors. In this case, some MOAHs can harm the endocrine system, causing damage to certain body tissues.

How can we prevent my oil from getting contaminated with hydrocarbons?

To address the issue, we must first trace it back to its source. Numerous studies have proven that the levels of MOSH in hand-picked olives are almost negligible, and the levels of MOAH are unquantifiable. So, when does the oil get contaminated with these substances?

Primarily during harvesting.

Accidental leaks of lubricants or contact with lubricated mechanical parts have been identified as major sources of contamination. Lubricants and hydraulic oils used in tractors or shakers could come into contact with the fruit, as well as jute or raffia sacks which, if not properly treated, may release mineral oils when they touch the olives. Equipment such as mills, mixers, and centrifuges might also have lubricant oil leaks that contain MOSH and MOAH. Additionally, some materials used in filtration and cleaning may contain hydrocarbons derived from petroleum.

Examples of Areas of Major Pollution Hotspots

Receiving Hoppers

A clear example of a pollution source would be the ground-level hoppers over which a tractor or a trailer-towed vehicle drives to unload goods. As the vehicle goes over the receiving hopper, it could leak engine oil, contaminating both the olives and the hopper itself.

Transportation and Packaging

Transportation can be one of the main sources of mineral oil hydrocarbon contamination. Therefore, tanker trucks used for transporting oil or any other substance must be thoroughly disinfected, since if they have previously carried substances contaminated with MOSH (Mineral Oil Saturated Hydrocarbons) or MOAH (Mineral Oil Aromatic Hydrocarbons), they could also contaminate the olive oil. The same applies to containers.

Harvesting

Another critical point of contamination in our olive oil is the harvesting process, as in many cases farmers carry their equipment like shakers, blowers, or chainsaws on the same trailer that they use to transport their harvest to the mill.

A good solution to this problem, or at least to reduce it, would be the use of sanitized boxes to transport the olives to the mill. This practice is not very common, but it's gradually becoming more appealing to farmers who care about the quality of their product.

Conclusion

The presence of MOSH and MOAH in olive oil is a challenge that the industry cannot overlook. While current levels do not pose an immediate risk in every case, scientific evidence and European regulations suggest that there will be tighter controls in the years to come.

Ensuring the quality and safety of olive oil is not only a legal requirement but also an opportunity to strengthen consumer confidence in a staple of our diet. Prevention starts on the farm, continues at the mill, and ends with packaging.

Investing in good practices, traceability, and analytical control will be essential to guarantee an oil free of contaminants and with all its value preserved.

Author: Ramsés Martínez Carrillo

March 29, 2025

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