Formation mechanisms of Monochloropropanediol (MCPD) fatty acid diesters in refined palm (Elaeis guineensis) oil and related fractions

Abstract

Monochloropropanediol (MCPD) fatty acid esters are process contaminants generated during the deodorisation of edible oils. In particular, MCPD diesters are found in higher abundance in refined palm oil than other edible oils. In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure acylglycerols in the presence or absence of either organic or inorganic chlorine-containing compounds. Results showed that the bulk of MCPD diesters are formed above 200°C through the reaction of organochlorines with triacylglycerols (TAG). Additional experiments confirmed that this reaction can be initiated during palm oil deodorisation by hydrogen chloride (HCl) gas evolved through the thermal degradation of organochlorines present in the oil. Therein, the majority of the ultimately produced MCPD diesters are the result of HCl reacting with TAG, via protonation, followed by the elimination of a fatty acid residue. Two possible MCPD diester formation mechanisms are highlighted, both of which involve acyloxonium ion reactive intermediates. Investigations with pure TAG regio-isomers showed that MCPD ester formation is regioselective and the sn-1(3) position of the glycerol backbone is favoured.

Chloropropanols, Chloropropandiols and Their Esters in Food – Formation, Occurrence, Determination, Reduction of Content

“…Glicydol (2,3-epoksy-propan-1-ol) w obecności HCl i pod wpływem ciepła może ulegać interkonwersji pomiędzy 3-MCPD i 2-MCPD. Mechanizmy powstawania MCPD i DCP oraz ich estrów zostały przedstawione w wielu publikacjach [9,14,34,59,60,67,71]. Analizowana jest także możliwość udziału związków chloroorganicznych rozpuszczalnych w fazie olejowej w powstawaniu 3-MCPD i jego estrów [53,58].…”

“…Destaillats i wsp. [14] wykazali, że w temp. >150 °C i w warunkach symulujących odwanianie triacyloglicerole (TAG), czyli główny składnik olejów roślinnych, są najbardziej reaktywnymi substratami w reakcjach powstawania diestrów MCPD.…”

Characterization of Electron Ionization Mass Spectral (EIMS) Fragmentation Patterns of Chloropropanol Esters of Palmitic Acid Using Isotope Labeling Technique

“…3 . The same ion series has also been observed under various soft ionization conditions 1,12 and has been referred to in the literature as diacylglyceride ions . This ion series could have great diagnostic utility during the analysis of CP esters 12 .…”

“…The high temperature of the refining process results in the interaction between triacylglycerides 1 and the naturally occurring organic and/or inorganic chlorine compounds in the crude oil 2 leading to the formation of CP esters. Current practice of CP ester detection consists predominantly of two approaches: direct and indirect 3 .…”

Organic or not organic – that is the question: How the knowledge about the origin of chlorinated compounds can help to reduce formation of 3‐MCPD esters

“…On the other side it helps to improve the development of mitigation strategies for the formation of 3-MCPD esters. Thus, the introduction of a washing step by Matthäus et al [3] was the right approach, but it is only the work of Nagy et al [4] and Destaillats et al [7] that explains the background for the effect that the washing has.…”