3-MCPD esters in refined edible fats and oils - a newly recognized global problem.
Where do the 3-MCPD esters come from?
Results to date have shown that 3-MCPD esters are formed primarily during refining. The refining of edible fats and oils is a multi-step chemical and physical process by which crude oils, inedible in this state, are rendered usable and preservable for human consumption. The vast majority of all edible fats and oils consumed as such or used as an ingredient in other foods are refined. The main process steps in a refining operation are degumming (removal of lecithin and mucilage), deacidification (removal of free fatty acids), and bleaching (removal of colorants and oxidation products). The final refining step is usually deodorization. This involves steam distillation under reduced pressure at temperatures up to 250°C to remove undesirable odors and flavors.
Further clarification of which sub-step of the refining process produces the main amount of 3-MCPD esters was carried out in close cooperation with the Institute of Lipid Research at the Federal Research Centre for Nutrition and Food (BFEL).
The jointly conducted tests led to the unambiguous result that in edible fats and oils almost the entire amount of 3-MCPD esters is formed only in the last step of refining, deodorization.
For a long time, 3-MCPD was only known to be present in seasoning sauces and baked goods. Recently, however, it was discovered that this substance, bound to fatty acids in the form of 3-MCPD esters, is formed in considerable quantities during the refining of edible fats and oils. In contrast, virgin edible oils are free of 3-MCPD esters. Since refined fats and oils are not only consumed as such, but are also included as an ingredient in many other foods, 3-MCPD esters are also widely distributed. At the moment, however, it cannot yet be definitively assessed whether this may have a detrimental effect on consumer health, as a final risk assessment of 3-MCPD esters is still pending.
The Federal Institute for Risk Assessment issued an initial statement on December 11, 2007, concluding that the levels must be reduced, but that there is no acute health risk.
What is 3-MCPD?
3-Chloro-1,2-propanediol (3-MCPD) is a substance that has been known as a contaminant in various foods since 1978. At first, 3-MCPD was thought to be found mainly in certain seasoning sauces made by hydrolyzing vegetable protein with hydrochloric acid. Over time, however, it became apparent that this substance is also formed during the production of baked goods or during the toasting of bread. In 2006, food chemists at CVUA Stuttgart discovered that 3-MCPD is also formed during the smoking of food (see article: 3-monochloropropanediol (3-MCPD) in smoked meat products).
So far, only so-called free 3-MCPD has been determined in foods within the scope of official monitoring. There is an EU limit of 20 µg/kg for free 3-MCPD, valid for soy sauce and for vegetable protein hydrolysate (HVP).
In 2001, the EU Commission's Scientific Committee on Food (SCF) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) established a tolerable intake (TDI) for (free) 3-MCPD of 2 µg per kg body weight per day. 3-MCPD has been shown to cause tumors in rats at high doses.
Free 3-MCPD has only been detected in edible fats and oils at trace levels below 10 µg/kg. However, in 2006, researchers at the University of Prague found that edible oils may contain high levels of 3-MCPD fatty acid esters, hereafter referred to as 3-MCPD esters.
What are 3-MCPD esters and where do they occur?
3-MCPD esters are compounds of 3-MCPD and various fatty acids, they are formed at high temperature by a reaction of fat components with chloride ions.
Shortly after the publication of the findings from Prague, the CVUA Stuttgart began to deal intensively with the topic. After first decisively improving the existing analytical procedure, more than 150 samples of fats, oils and fat-containing foods have so far been analyzed for 3-MCPD esters. The most important findings of the investigations are summarized in the figure and can be interpreted as follows:
Virgin and cold-pressed vegetable oils
No 3-MCPD esters were detected in any of the native vegetable oils tested to date, including, for example, olive oils in the "extra virgin" category. This was not to be expected otherwise, because native edible oils must not be subjected to any heat treatment during production.
Vegetable oils advertised as "cold-pressed" contained 3-MCPD esters in only a very few cases. The cold-pressed oils with a noticeable content of 3-MCPD esters were most likely subjected to treatment with steam (steaming). Steaming of cold-pressed oils is widely used, and the steaming conditions (temperature and time) have a wide range of variation. The test results suggest that only relatively drastic steaming conditions produce larger amounts of 3-MCPD esters.
The test results for cold-pressed sesame oils, walnut oils, and pumpkin seed oils suggest that only very small amounts of 3-MCPD esters are formed during roasting (and probably drying) of oilseeds.
Refined vegetable oils
Without exception, all refined vegetable oils investigated contain 3-MCPD esters, in very different, sometimes very high levels. The highest levels were found in a refined walnut oil and a refined grape seed oil.
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