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Acyloxonium ions formation in palmitin systems

Twenty years ago, cyclic acyloxonium ions were proposed as an intermediate in the formation of free chloropropanols. To confirm the possible involvement of cyclic acyloxonium ions in the transformations of food TAG into chloropropanols, Rahn et al. [330–334] monitored the formation of cyclic acyloxonium ions in palmitin systems using FTIR and isotope labeling. The absorption band of acyloxonium ions was centered at 1651 cm−1. The esterified and free acyloxonium ions could not be distinguished by IR spectroscopy, but the release of pamitic acid in 1,2-dipalmitoyl-rac-glycerol samples indicated that acyloxonium ion formation occurs between two neighboring ester groups. This is the first time that the formation of acyloxonium ions has been monitored in food related lipid system, which provides further evidence for their possible involvement as reactive intermediates in the generation of 3-MCPD and its esters in edible oils.

Rahn, A. K. K. et al., Eur. J. Lipid Sci. Technol. 2011, 113, 330–334

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Can reducing DAG help reducing 3-MCPD?

Three strategies are conceivable in order to reduce the burden of 3-MCPD esters and related compounds in edible fats and oils: (i) removing the critical reactants from the raw materials, (ii) preventing their formation by changing the refining process, or (iii) removing the formed 3-MCPD esters from the refined product. Matthäus et al. [380–386] discuss these possibilities and show that palm, corn, and coconut oils have the highest potential for the formation of 3-MCPD esters and related compounds. Washing the raw material before the refining process with water or ethanol reduced the formation of 3-MCPD esters and related compounds in palm oil by 20–25%. The authors show that chloride and DAGs are important precursors for the formation of 3-MCPD esters and hypothesize that a 4% level of DAGs could be a threshold for a higher potential of the raw material for the formation of the esters. In addition, they demonstrated that using acid solutions instead of water for the generation of strip steam during the deodorization results in a reduction of the formation of glycidyl esters by about 35%.

Matthäus, B. et al., Eur. J. Lipid Sci. Technol. 2011, 113, 380–386

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Simultaneous determination of bound MCPD and glycidol

Kuhlmann [335–344] presents a new method for simultaneous determination of bound glycidol (limit of detection 0.025 mg/kg in absence of 3-MCPD) and 2- or 3-MCPD in oil matrices. Existing methods are not suitable for parallel determination of bound glycidol and bound MCPD in one step, or provide an estimation of bound glycidol by calculation only. Kuhlmann's method is based on an improved alkaline catalysed release of MCPD and glycidol followed by a transformation of glycidol to monobromopropanediol (MBPD), derivatisation with phenylboronic acid (PBA) and analysis by GC–MS. Quantification was performed using isotope labeled standards. The method was validated using glycidyl stearate and 3-chloropropanediol-1,2-bis-palmitoyl ester as reference compounds.

Kuhlmann, J. Eur. J. Lipid Sci. Technol. 2011, 113, 335–344

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