Esters of monochloropropanediol (MCPD) and glycidol are process contaminants that can be formed during the high temperature deodorization of edible oils and are under evaluation as suspect carcinogens. A body of research on laboratory model chemical reactions mimicking oil deodorization conditions has been conducted with pure acylglycerols in the presence or absence of organic and inorganic chlorine-containing compounds. Results showed that MCPD esters (ME) are formed at temperatures as low as 150 °C, most often through the reaction of organochlorines with TAG. Additional bench-top experiments confirmed that this reaction could be initiated during palm oil deodorization by hydrogen chloride (HCl) gas evolved through the thermal degradation of multiple lipophilic organochlorines present in refined-bleached palm oil. Statistical evaluation of analytical results showed a correlation between organochlorine type and oil refining stage suggesting that these compounds are undergoing a transformation throughout oil production. The majority of MCPD esters formed during deodorization are a result of HCl reacting with TAG at ≥200 °C. This reaction is regioselective and the sn-1(3) position of the glycerol backbone is favored at about a 75-80% frequency. Glycidyl esters (GE) on the other hand, are beginning to be formed at temperatures above 200 °C from DAG (and MAG if present), but not often from TAG, and accumulate exponentially when beyond 3-4% DAG levels in the refined-bleached oil. This level of DAG corresponds to ~2 to 2.5 % of free fatty acids (FFA) in crude palm oil (CPO). Isomers of GE, identified as oxopropyl esters, are also formed during oil deodorization and contribute to around 10% of GE levels. This presentation will focus on the impact this completed research has had on strategies to mitigate the levels of these process contaminants throughout the production and supply chain of refined vegetable oils. Whilst many suppliers of refined edible oils, like palm, have been successful at mitigating ME & GE during oil refining (particularly deodorization), the completed research suggests that precursor-focused mitigation efforts upstream at oil crop harvest and pressing may be more impactful. Further, the combination of both precursor-and refining-focused mitigation efforts together in certain crops like palm oil, may be the only way to achieve the near elimination of these process contaminants.

MCPD- and glycidyl-esters in palm oil: Mechanisms of formation and opportunities for effective mitigation

254th National Meeting (2017)

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