3-monochloropropane diol (3-MCPD), 3-MCPD esters and glycidyl esters

October 2018

3-MCPD is the most commonly occurring group of contaminants known as chloropropanols. First identified as a contaminant of acid-hydrolysed vegetable proteins and soy sauce, it was later found in other foods. 3-MCPD and its esters can be formed in heat processed fat-containing foods from glycerol or acyl glycerides, in the presence of chloride ions. Glycidyl fatty acid esters (GEs) are processing induced contaminants primarily found in refined fats and oils, and foods containing fats and oils. Initially it was assumed that 3-MCPD esters and GE’s were formed by similar processes, but it is now known that their mechanisms of formation are different. Both substances are considered to be of concern to public health and it is recommended to minimize the amount consumed. Further information is provided in the section on public health significance and useful background and information can be found in the references.

What is 3-MCPD and how does it form?

3-MCPD is a contaminant first identified in acid-hydrolysed vegetable proteins and soy sauce. It is the most commonly occurring group of contaminants known as chloropropanols which are also found present in certain foods, often at much higher levels. These compounds relate structurally to 3-MCPD and are formed by similar processes.

What are GEs and how are they formed?

GE formation is directly associated with elevated temperatures and how long they are at these temperatures. They are generally formed from diacylglycerols with no requirement for the presence of chlorinated compounds.

Formation of 3-MCPD and related substances

3-MCPD is formed as a result of a reaction between a source of chlorine, e.g. chlorinated water or salt, in a food or a food contact material, and a lipid source. This reaction is encouraged during the heat processing of foods, including roasting, frying and baking. It is also known to occur in acid-hydrolysed vegetable protein (HVP) when produced using hydrochloric acid. Once formed, the stability of 3-MCPD has been shown to be dependent upon the pH and temperature to which it has been exposed. The higher the pH and temperature of the heat treatment, the greater the rate of 3-MCPD degradation. During the production of fats and oils, 3-MCPD fatty acid esters may be formed from 3-MCPD when the fats and oils are heated to high temperatures, in the presence of chloride ions. GEs are mainly formed from diglycerides at temperatures above 230oC.

Occurrence of 3-MCPD and related substances in foodstuffs

3-MCPD and related substances have been found in a wide range of foods, with the highest levels being in fats and oils, as reported in the EFSA study: ‘3-MCPD occurrence in food in Europe’.  Other foodstuffs also reported included: foods for infants and small children; composite foods; grains and cereal based products; herbs; condiments; dressings; meat and meat products; potato and potato products; protein and amino acid supplements.  In cereal derived products it is understood that commonly added salt is one of the major precursors and glycerol another.  Glycerol and chloride react together during the baking stage to form 3-MCPD.  Other compounds also form 3-MCPD on reaction with chloride, various substituted glycerols and phospholipids.  Fatty acid esters of 3-MCPD have been found in high levels in refined edible oils and fats and derived foods, including milk powder for infants by the German control authorities.

Contributors to be possible factors in 3-MCPD and related substance formation include:

  • naturally occurring levels in raw materials
  • storage of raw materials
  • use of chlorinated water for washing purposes
  • the level of diacetyl glycerol (DAG) and polar compounds in fats and oils
  • high temperatures during processing
  • commercial food processing including baking, evaporation, fermentation, malting, pasteurisation, roasting, smoking, spray drying, sterilisation and UHT
  • migration from food contact materials
  • storage of prepared products
  • domestic food preparation including baking, boiling, frying, grilling and toasting.
Public Health Significance

In 2016 the Joint WHO/FAO Expert Committee on Food Additives (JECFA) concluded that 3-MCPD esters are substantially hydrolysed to 3-MCPD in the gastrointestinal tract, delivering the same toxicity as free 3-MCPD. No genotoxic potential has been demonstrated for free 3-MCPD. Based on these findings, JECFA published a Tolerable Daily Intake (TDI) of 4 µg/kg of body weight per day, or 3-MCPD and its esters, singly or in combination, expressed as 3-MCPD equivalents. Following this review, EFSA has reissued a TDI of 2 µg/kg of body weight per day for 3-MCPD. JECFA noted that the estimated dietary exposures to 3-MCPD for the general population did not exceed the Provisional Maximum Tolerable Daily Intake (PMTDI), however in formula fed infants, the PMTDI may be exceeded. JECFA have not set a TDI for GE’s based on evidence that they are genotoxic carcinogens. In the gastrointestinal tract the esters are substantially hydrolysed to glycidol and exhibit toxicity as such.

Legislation

European Commission Regulation (EC) No1881/2006 prescribes maximum levels of 3-MCPD of 0.02 mg/kg (20μg/kg) for HVP and soy sauce.  In the case of the soy sauce, the limit is based on a product containing 40% dry matter [corresponding to a maximum level of 0.05mg/kg (50μg/kg) in dry matter].

This has since been revised with (EC) 290/2018 setting maximum levels for GE’s in vegetable oils and fats: 1,000μg/kg for the general population; 500μg/kg in baby foods and processed cereal based food for infants and young children, with lower levels set for infant formulae and foods for special medical purposes intended for infants and young children.

Detection

The American Oil Chemists’ Society (AOCS) have published methods available for GEs and 3-MCPD and related esters applicable to fats and oils (2). A method available to detect GEs uses double solid-phase extraction (SPE) and liquid chromatography mass spectrometry (LC-MS). The method available for the parallel determination of glycidol, together with 2-MCPD and 3-MCPD present in bound or free form, is based on alkaline-catalyzed ester cleavage, transformation of the released glycidol into monobromopropanediol (MBPD) and derived free diols (MCPD and MBPD) with phenylboronic acid (PBA).

Industry good practice

In cases where the mechanism of formation is understood, measures can be taken to reduce the levels of the precursors and adapt processing conditions to reduce overall levels in the finished product.  Any reduction measures need to ensure a comprehensive HACCP review considering impact to chemical, microbiological and physical hazards for the target consumer group. In addition to quality parameters and consumer acceptance which also need to be reviewed.

Terms used

3-monochloropropane-1,2-diol (3-MCPD)

2-monochloropropane-1,2-diol (2-MCPD)

Glycidyl fatty acid esters (GEs)

Hydrolysed vegetable protein (HVP)

Diacetyl glycerol (DAG)

Tolerable daily intake (TDI)

Provisional maximum tolerable daily intake (PMTDI)

American Oil Chemists’ Society (AOCS)

Solid phase extraction (SPE)

Liquid chromatography mass spectrometry (LC-MS)

Monobromopropanediol (MBPD)

Phenylboronic acid (PBA)

Hazard Analysis Critical Control Points (HACCP).

References

JECFA Report on Glycidyl esters http://www.fao.org/3/a-bq821e.pdf

JECFA Report on 3-MCPD

JECFA report on 3-MCPD esters

EFSA report on 3-MCPD

http://ec.europa.eu/food/food/chemicalsafety/contaminants/mcpd_en.htm 

  • Legislation EC 1881/2006
  • Sampling and analysis EC 333/2007
  • Scientific opinions
  • ILSI 3 MCPD esters workshop presentations
  • SCOOP report chloropropanols in food

https://www.aocs.org/attain-lab-services/methods/methods/search-results?method=111541

Direct Determination of MCPD Fatty Acid Esters and Glycidyl Fatty Acid Esters in Vegetable Oils by LC-TOFMS by ADM as published in JAOCS. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3022155/ 

http://www.bfr.bund.de/cm/279/frequently_asked_questions_about_3_monochloropropane_1_2_diol.pdf 

  • Focus on risk assessment of 3 MCPD esters
  • Risk assessment of 3MCPD esters in food

 http://europe.ilsi.org/events/past/Workshop3MCPDesters.htm 

  • International workshop on 3 MCPD esters

 http://www.food.gov.uk/search/?q=3mcpd 

  • FSA
  • Background information
  • Occurrence in foods
  • Incidents
  • COT report
  • Research study

Strategies for the reduction of 3-MCPD esters and related compounds in vegetable oils Bertrand Matthäus1*, Frank Pudel2, Peer Fehling2, Klaus Vosmann1, Anne Freudenstein1 FSA FEI research program

Fatty acid esters of chloropropanols and related compounds in food: Toxicological aspects Benoit Schilter, Gabriele Scholz, Walburga Seefelder

Nestle paper can be found in:

Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2008 Apr; 25(4):391-400.

Esters of 3-chloro-1,2-propanediol (3-MCPD) in vegetable oils: significance in the formation of 3-MCPD.

Seefelder W, Varga N, Studer A, Williamson G, Scanlan FP, Stadler RH.

Further paper on in vivo absorption of 3 MCPD esters:

Buhrke, T., Weißhaar, R., and Lampen, A., Absorption and Metabolism of the Food Contaminant 3-Chloro-1,2-propanediol (3-MCPD) and its Fatty Acid Esters by Human Intestinal Caco-2 Cells, Archives of Toxicology: 1-8 (2011). Web 11 May 2011.

Institute of Food Science & Technology has authorised the publication of the following updated Information Statement on 3-monochloropropane diol (3-MCPD), 3-MCPD esters and glycidyl esters dated October 2018, replacing that of November 2014. 

This updated Information Statement has been prepared by Sarah Howarth CSci FIFST, peer reviewed by professional members of IFST and approved by the IFST Scientific Comittee. 

The Institute takes every possible care in compiling, preparing and issuing the information contained in IFST Information Statements, but can accept no liability whatsoever in connection with them. Nothing in them should be construed as absolving anyone from complying with legal requirements. They are provided for general information and guidance and to express expert professional interpretation and opinion, on important food-related issues.