title: Role of choline and glycine betaine in the formation of N,N-dimethylpiperidinium (mepiquat) under Maillard reaction conditions.
abstract: This study is the first to examine the role of choline and glycine betaine, naturally present in some foods, in particular in cereal grains, to generate N,N-dimethylpiperidinium (mepiquat) under Maillard conditions via transmethylation reactions involving the nucleophile piperidine. The formation of mepiquat and its intermediates piperidine - formed by cyclisation of free lysine in the presence of reducing sugars - and N-methylpiperidine were monitored over time (240°C, up to 180 min) using high-resolution mass spectrometry in a model system comprised of a ternary mixture of lysine/fructose/alkylating agent (choline or betaine). The reaction yield was compared with data recently determined for trigonelline, a known methylation agent present naturally in coffee beans. The role of choline and glycine betaine in nucleophilic displacement reactions was further supported by experiments carried out with stable isotope-labelled precursors (¹³C- and deuterium-labelled). The results unequivocally demonstrated that the piperidine ring of mepiquat originates from the carbon chain of lysine, and that either choline or glycine betaine furnishes the N-methyl groups. The kinetics of formation of the corresponding demethylated products of both choline and glycine betaine, N,N-demethyl-2-aminoethanol and N,N-dimethylglycine, respectively, were also determined using high-resolution mass spectrometry.
authors.affiliation: a Nestlé Research Centre , Lausanne 26 , Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bessaire
authors.forename: Adrienne
authors.initials: A
authors.lastname: Tarres
authors.forename: Richard H
authors.initials: RH
authors.lastname: Stadler
authors.forename: Thierry
authors.initials: T
authors.lastname: Delatour
mesh_terms: D000470:Alkaloids / Q000737:chemistry; D001622:Betaine / Q000737:chemistry*; D002250:Carbon Radioisotopes; D002794:Choline / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003903:Deuterium; D006358:Hot Temperature; D007700:Kinetics; D008239:Lysine / Q000737:chemistry; D015416:Maillard Reaction; D008745:Methylation; D008956:Models, Chemical; D015394:Molecular Structure; D008970:Molecular Weight; D010880:Piperidines / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D000470:Alkaloids; D002250:Carbon Radioisotopes; D010880:Piperidines; C009560:trigonelline; D001622:Betaine; D003903:Deuterium; D008239:Lysine; D002794:Choline; C049449:mepiquat
keywords: Maillard reaction; cereals; choline; glycine betaine; heat treatment; mepiquat; methylation; model system