Review: Processing Contaminants in Edible Oils: MCPD and Glycidyl Esters

Processing Contaminants in Edible Oils: MCPD and Glycidyl Esters

Processing Contaminants In Edible Oils

Edited by Shaun MacMahon

AOCS press, Illinois, 2014
ISBN 978-0-9888565-0-9.
230 pages.
Hardback. $110.00 USD

Amazon electronic version $85.00 USD

Industry, academia and legislators have awaited the publication of a book such as this for quite some time. Heightened awareness around the presence of fatty acid esters of monochloropropanediol in refined edible oils began in 2006 with a publication by Zelinkova.

This book was published following a key seminar to address this issue at an AOCS conference in 2011. The issue attracted intense scrutiny because of its occurrence in infant formulae with the source being the deodorised vegetable oils utilised in the blends.

Compiler and editor, Dr. Shaun MacMahon, is a research chemist with the USFDA.

3-Monochloropropanediol (3-MCPD) esters, 2-monochloropropanediol (2-MCPD) esters and glycidyl esters (GEs) are contaminants that are not present in virgin unrefined oils but can be produced during processing, specifically during high temperature deodorisation.

Where did the chlorine atoms come from?
The book consists of 7 chapters, 10 authors and comprises 230 pages of extremely useful information. When the topic of these contaminants emerged a key question arose as to the source of chlorine atoms. Hypotheses and proposals which seem logical are proposed in the first chapter.
Chlorine atoms are sourced either from chlorides in the soil, from marine origins, or from added fertilisers or pesticides. While the mechanisms of the formation of these contaminants have not been conclusively elucidated, there is evidence suggesting that 3-MCPD esters are formed from iron chloride in the soil and/or natural organochlorine compounds. Before an accurate risk assessment of these contaminants in food can be made, detailed, accurate, and repeatable analyses must be established.
Analytical methods for contaminants
About 50% of the book is dedicated to a systematic and very detailed description of these different analytical methods. They fall into two categories: indirect and direct methods. In the early years of these contaminant analyses, trial indirect methods of transesterification were used and results were ambiguous and distrusted by industry. The chapters on direct methods, by both MacMahon and German researchers Alice Thürer and Michael Granvogl, summarise the current techniques utilising liquid chromatography and time-of-flight mass spectrometry. Following accurate direct methods, a great deal of work has subsequently occurred to validate indirect techniques. The establishment of standard AOCS methods (AOCS, 2014) greatly assists in this development. Ranges of levels found in vegetable oils, from 0.5 ?g/g (ppm) to 40 ?g/g, are presented. Deodorised palm and grape seed oils appear to have the highest levels recorded.
Management of contaminants

Mitigation strategies that have been used successfully to decrease the concentrations of these contaminants in edible oils are discussed in the second chapter. These include removing precursor molecules before processing, using alkaline additives before deodorising, adding ethanol to the oil, and using selective adsorbents.

The fact that MCPD esters begin forming at temperatures exceeding 200°C makes mitigation difficult because deodorisations with physical refining are generally run at temperatures greater than 200°C.

It is a small oversight, probably due to timing of the compilation, that the book does not have any extra reported work from edible oil practitioners who have experience in changing process conditions to observe changes in contaminant levels. Such work was presented at AOCS seminars in 2012 and 2013 (De Greyt, 2012). Practical economic techniques, suggested by process suppliers such as Desmet, are assisting the edible oil industry in reducing levels to acceptable amounts. This practical work will no doubt be presented at future AOCS conferences and seminars.


The toxicology of glycidyl esters and of the MCPD fatty acid esters is dealt with in two chapters reporting work on the two classes of compound separately. Any toxic effects are due to the products after metabolism in the gut.

Free 3-MCPD and glycidol have been shown to be carcinogenic in rats, with demonstrated effects on kidneys and reproductive systems. Glycidol is well characterised due to its use in the chemical industry. 3-MCPD and glycidol were classified by the European Scientific Committee on Food in 2001 as a non-genotoxic threshold carcinogen. Toxicology is dealt with in a detailed way in the last two chapters of the book by researchers

Areas of interest for the future
There is no separate chapter on legislation, either by the US FDA or the European Food Safety Authority (EFSA), and one may assume that legislators are still working through key issues such as the breakdown rate of the esters by gut lipases into free MCPD and glycidol plus arriving at sensible maximum allowable levels in oils and foods containing them. The final chapter in the book, on toxicology, summarises the situation by stating that several important questions remain to be resolved such as the rate of hydrolysis of MCPD esters in humans. Risk assessment can only be done and legislative standards established when analyses become totally reliable and well established in multiple laboratories around the world. Current trading standards, especially for palm oil, are for total glycidyl and MCPD esters to be <2 ppm with <1 ppm for oils destined for infant formulae.
The book is well presented and laid out with a comprehensive index and extensive references with each chapter, and no errors were detected. It is good value for money and should be a foundation work for anyone in this area. The information in this book is rapidly being updated with other reported material in this vital area for edible oil processors and food manufacturers alike (EFSA, 2013).
Useful references

Zelinková, Z., B. Svejkovská, J. Velí?ek, and M. Dole?al, Fatty acid esters of 3-chloropropane-1,2-diol in edible oils, Food Addit. Contam. 23:1290?1298 (2006).

Analysis of occurrence of 3-monochloropropane-1,2-diol (3-MCPD) in food in Europe in the years 2009?2011 and preliminary exposure assessment, European Food Safety Authority Journal 11(9):3381 [45 pp.], 2013. http://dx.doi. org/10.2903/j.efsa.2013.3381.

De Greyt, W., How to minimize 3-MCPD- and Glycidyl Esters during Edible Oil Processing, Paper presented to AOCS seminar, Korea, May 11-12th (2012)

AOCS Standard Methods Cd 29a-13 (2- and 3-MCPD fatty acid esters and glycidol fatty acid esters in edible oils and fats by acid transesterification),

Cd 29b-13 Determination of bound monochloropropanediol- (MCPD) and bound 2,3-epoxy-1-propanol (glycidol-) by gas chromatography/mass spectrometry),

Cd 29c-13 (Fatty-acid-bound 3-chloropropane-1,2-diol (3-MCPD) and 2,3-epoxypropane- 1-ol (glycidol), Determination in oils and fats by GC/MS (differential measurement)), 2014.

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Reviewer, Dr Laurence Eyres, FNZIFST, runs his own contracting/consulting business for the Food and Dietary Supplements Industries specialising in dairy, oils and fats and related lipids, product and business development. He has been a member of AOCS since 2002.

Download a copy of this review as it appeared in Food New Zealand, June/July 2014 issue:

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