MECHANISMS OF FORMATION OF ALKYLPYRAZINES IN THE MAILLARD REACTION

The formation of alkylpyrazines was investigated in the reaction of glucose and fructose with [3-C-13]alanine and [2-C-13]glycine. The reaction systems were heated for 7 min at 180 degrees C. GC-MS and GC-MS/MS data were used to determine the rate of incorporation and the position of isotopic labeling in the pyrazines formed. The results show that alanine and glycine not only act as the nitrogen source but also contribute to the alkyl side chain of some alkylpyrazines. While glycine was involved in one of the methyl groups of trimethylpyrazine, alanine contributed the C2 element in the ethyl groups of ethylmethyl-, ethyldimethyl- and diethylmethylpyrazines. The proposed reaction routes include the addition of the Strecker aldehydes of alanine and glycine to dihydropyrazines, which are postulated as intermediates.