Role of the solvent glycerol in the Maillard reaction of d-fructose and l-alanine.
The volatiles in the headspace above a solution of [(13)C(6)]fructose and alanine in glycerol/water, heated in a closed vial at 130 degrees C for 2 h, were analyzed by solid-phase microextraction in tandem with GC-MS. Carbonyl compounds and pyrazines were among the detected components. The examination of their mass spectra showed that most of the 1-hydroxy-2-propanone and 2,3-pentanedione were (13)C(3)-labeled, the majority of the 2-methylpyrazine and 2-ethyl-3-methylpyrazine were (13)C(5)-labeled, and 2,5-dimethylpyrazine and 3-ethyl-2,5-dimethylpyrazine were mainly (13)C(6)-labeled. This is in agreement with the literature, and corresponds to the incorporation of fructose carbons, and in the case of 2,3-pentanedione, 2-ethyl-3-methylpyrazine, and 3-ethyl-2,5-dimethylpyrazine alanine carbons, into the molecules. However, minority fractions of 1-hydroxy-2-propanone (10%) and 2,3-pentanedione (14%) were found unlabeled, 2-methylpyrazine (10%) and 2-ethyl-3-methylpyrazine (11%) only doubly labeled, and 2,5-dimethylpyrazine (20%) and 3-ethyl-2,5-dimethylpyrazine (27%) only triply labeled, suggesting they contain carbons originating from the solvent glycerol. This could be confirmed by reaction of fructose and alanine in [(13)C(3)]glycerol/water, which produced the same volatiles, with 11-27% existent in their (13)C(3)-labeled form. Hence, glycerol participated not only as a solvent but also as a precursor in the reaction.
Cerny
Christoph
C
Corporate R and D Division, Firmenich SA, P.O. Box 148, 1217 Meyrin 2, Geneva, Switzerland. christoph.cerny@firmenich.com
Guntz-Dubini
Renée
R
D000409:Alanine / Q000737:chemistry*; D005632:Fructose / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D005990:Glycerol / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D015416:Maillard Reaction; D012996:Solutions; D012997:Solvents / Q000737:chemistry*; D014835:Volatilization; D014867:Water
D012996:Solutions; D012997:Solvents; D014867:Water; D005632:Fructose; D000409:Alanine; D005990:Glycerol