7 minute read
The next processing challenge
The past three decades have seen increasing att enti on paid to contaminants in food oils.
The 1990s saw a focus on trans fatt y acids (TFAs) and pesti cides, while the 2000s witnessed a shift to dioxins, polychlorinated biphenyls (PCBs) and polycyclic aromati c hydrocarbon (PAHs), Antonios Papastergiadis of Desmet Ballestra told the 25th Practi cal Short Course on Advanced Oils & Fats Processing and Applicati on Technology on 15-17 November. In the 2010s, att enti on focused on 3-monochloropropane diol (3MCPD) and glycidyl esters (GEs), and the 2020s is seeing more focus on mineral oil and phthalates contaminati on (see Figure 1, below).
Mineral oil hydrocarbons (MOH)
e next processing challenge
MOSH and MOAH are mineral oil hydrocarbons that can contaminate oils and fats in all stages of the production chain. While steps can be taken to mitigate their presence before processing, only deodorisation can remove them during re ning
encompass a wide range of products derived from petroleum disti llati on facti ons, according to Giorgia Purcaro, an analyti cal chemistry professor at the Gembloux Agro-Bio Tech Department at Belgium’s University of Liège.
They comprise mainly mineral oil saturated hydrocarbons (MOSH) and mineral oil aromati c hydrocarbons (MOAH).
Being non-polar molecules, MOSH and MOAH have excellent miscibility with oils and fats, and are the main consti tuents of mineral oil lubricants, according to Papastergiadis.
Potenti al sources of MOSH/MOAH contaminati on can come from the environment; crop harvesti ng; during transportati on of seeds and crude oils; during oil extracti on and refi ning; and from packaging (see Figure 2, below).
Although the presence of MOH in u
Environment
Source: Desmet Ballestra
Packaging
Sources of contamination Agricultural practi ces/ harvesti ng
Oil extracti on/ refi ning Transport of seeds/ crude oils
Figure 3: MOSH/MOAH mitigation – removal during refining
Source: Desmet Ballestra
CONDENSATE
Figure 4: Continuous dual temperature deodoriser for low MOSH/MOAH, GE, TFAs
Source: Desmet Ballestra
u foods and their potential risk to human health has been known since the 1990s, it has only been in the last 10-15 years that it has become the object of more studies to understand its toxicological relevance, improve analytical methods, and to legislate its presence in food, Purcaro told the18th Euro Fed Lipid Congress in October last year.
Attention also became widespread in 2008/2009 following the discovery of contaminated sunflower oil in Ukraine.
Exposure and risk
In 2012, the European Food Safety Authority (EFSA) published a scientific opinion on mineral oil hydrocarbons (MOH) in food and although no tolerable daily intake (TDI) for MOH could be established due to insufficient data, it was concluded that exposure to MOH via food intake in Europe was of potential concern.
MOAH may act as a genotoxic carcinogen, while some MOSH can accumulate in human tissue and may cause adverse effects in the liver, according to the Dutch National Institute for Public Health and the Environment (RIVM).
In its 2019 report, ‘Mineral Oils in Food: a Review of Occurrence and Sources’, the institute said new studies mostly reported MOSH concentrations of below 10mg/ kg, with the highest mean concentrations of MOSH reported for pasta, cocoa powder, coffee, tea, chocolate flakes and sweets. For MOAH, most measured concentrations were below 0.5mg/kg with some exceptions exceeding 2-3mg/kg in pasta, vegetable oils, chocolate flakes, cocoa and coffee beans.
There had been an overall decline of mineral oil contaminations since the 1990s due to the identification of mineral oil contamination sources and mitigation measures, the RIVM report said.
Examples of successfully-reduced sources of mineral oil contamination included the use of jute bags treated with batching oil; the application of (white) mineral oils as glazing agents, release agents in industrial bakeries and additions to animal feed; different contaminations of edible oils; and the migration from paperboard packaging.
Because of this decline, the relative contribution of environmental contamination may have increased. Exact data on what sources were causing mineral oil contamination in food today was still missing, the RIVM said.
So far, no tolerable daily intake levels (TDIs) for MOSH or MOAH have been set in the EU but the EFSA is working on a new scientific opinion on the toxicity of MOSH and MOAH, which is expected to be released this year, Papastergiadis told the Practical Short Course in November.
The opinion may include a TDI value for MOSH, and a ‘as low an intake as possible’ value for MOAH. Meanwhile, the German Food Federation has a maximum level of 13ppm for MOSH and 1ppm for MOAH.
MOSH/MOAH mitigation
Avoiding MOSH/MOAH contamination via the environment is very difficult, according to Papastergiadis.
During cultivation and harvesting, contamination may occur from machinery oil leaks and exhaust emissions.
During transport of seeds and crude or refined oil, cross-contamination may come from the transportation carrier, the use of inappropriate material for storage and transport of seeds (such as jute bags treated with batching oils) and antidusting agents.
During oil extraction and refining, leaks may come from processing machinery, and food grade lubricants should be used when possible, as well as non-contaminated processing aids. Contamination may also occur from solvent recovery systems.
And during packaging and bottling of final products, material should be used that do not migrate MOH to the oils and fats.
Removal during refining
MOSH/MOAH can be removed during refining but only in the deodorisation step (see Figure 3, above left), Papastergiadis said.
Stripping depended on the applied deodorisation conditions (temperature, pressure and stripping steam) and short chain C-fractions of MOSH/MOAH (up to C35) could be removed at levels of up to 80-90%. Successful overall removal depended on the origin of the contamination, with heavier C-fractions remaining problematic.
Desmet Balletra supplied the Qualistock+ deodoriser to achieve low levels of MOSH/MOAH, GEs and TFAs,
which could operate in dual-temperature mode (see Figure 4, left). Papastergiadis said. The integrated packed column stripper offered a short residence time, high temperature (240-2600C) and FFA and MOSH/MOAH stripping with some heat bleaching,
The tray type deodoriser operated with a longer residence time, lower temperature (220-2400C) with a final heat bleaching/deodorisation step. Deep vacuum (<2mbar) could be applied by either a closed loop chilled water system or ice condensing to increase stripping.
Papastergiadis said that deodorisation under optimised conditions could produce an oil with a bland odour and taste with a good shelf life, low FFAs and good heat bleaching with a light colour. It partially removed MOSH/MOAH but GE levels would be too high. Poststripping was therefore necessary at a lower temperature, with a deep vacuum for maximum MOSH/MOAH and GE removal.
An integrated scrubber led to minimum oil carry-over to the vaccum system, with deep vacuum (ice condensing) for efficient GE stripping and fast cooling under vaccum to avoid the reformation of GE and to keep the bland odour and taste.
Figure 5: Sublimax 2G ice condensing for deep vacuum deodorising/stripping
Conclusion
MOSH and MOAH are major components of mineral oil products and their presence is abundant and can contaminate oils and fats in all stages of the production chain. The removal of MOSH and MOAH during refining can only take place in the deodorisation step.
Suitable deodorisation conditions can lead to the removal of C-fractions up to C35 but heavier C-fractions remain a challenge. ●
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