Origin of carbons in sulfur-containing aroma compounds from the Maillard reaction of xylose, cysteine and thiamine

The Maillard reaction of cysteine and thiamine with reducing sugars is known to be important for the aroma generation both in meat and meat-like process flavourings. Headspace SPME analysis in combination with GC-MS was used to analyse the volatiles produced from a solution of [13C5]xylose, cysteine and thiamine, heated at 145 °C during 20 min. Analysis of the mass spectra showed that the resulting 2-furaldehyde and 2-furfurylthiol were 13C5-labeled and hence stem from xylose, whereas 3-mercapto-2-butanone, 4,5-dihydro-2-methyl-3(2 H)-furanone, 4,5-dihydro-2-methyl-3-furanthiol and 4,5-dihydro-2-methyl-3(2 H)-thiophene were virtually unlabeled suggesting their origin from thiamine. Xylose and thiamine were equally important for the formation of 2-methyl-3-furanthiol and 3-mercapto-2-pentanone, when cysteine was present in the reaction. In the absence of cysteine, however, both sulfur compounds were only formed from thiamine indicating that xylose did no longer play a role therewith emphasizing the role of cysteine as sulfur source.