title: Alkylpyridiniums. 1. Formation in model systems via thermal degradation of trigonelline.
abstract: Trigonelline is a well-known precursor of flavor/aroma compounds in coffee and undergoes significant degradation during roasting. This study investigates the major nonvolatile products that are procured after trigonelline has been subjected to mild pyrolysis conditions (220-250 degrees C) under atmospheric pressure. Various salt forms of trigonelline were also prepared and the thermally produced nonvolatiles analyzed by thin layer chromatography, liquid chromatography-electrospray ionization tandem mass spectrometry, and (1)H and (13)C nuclear magnetic resonance. Results revealed the decarboxylated derivative 1-methylpyridinium as a major product of certain salts, the formation of which is positively correlated to temperature from 220 to 245 degrees C. Moreover, trigonelline hydrochloride afforded far greater amounts of 1-methylpyridinium compared to the monohydrate over the temperature range studied. Investigations into other potential quaternary amine products of trigonelline also indicate nucleophilic substitution reactions that lead to dialkylpyridiniums, albeit at concentration levels approximately 100-fold lower than those recorded for 1-methylpyridinium.
authors.affiliation: Nestlé Research Center, Nestec Ltd., Vers-chez-les-Blanc, CH-1000 Lausanne 26, Switzerland. richard.stadler@rdls.nestle.com
authors.forename: Richard H
authors.initials: RH
authors.lastname: Stadler
authors.forename: Natalia
authors.initials: N
authors.lastname: Varga
authors.forename: Jörg
authors.initials: J
authors.lastname: Hau
authors.forename: Francia Arce
authors.initials: FA
authors.lastname: Vera
authors.forename: Dieter H
authors.initials: DH
authors.lastname: Welti
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D000478:Alkylation; D002247:Carbon Isotopes; D003069:Coffee; D003296:Cooking; D006358:Hot Temperature; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy; D011726:Pyridinium Compounds / Q000032:analysis*; D013649:Taste; D013816:Thermodynamics
chemical_list: D000470:Alkaloids; D002247:Carbon Isotopes; D003069:Coffee; D011726:Pyridinium Compounds; C009560:trigonelline; C014677:1-methylpyridinium; D006859:Hydrogen