On the significant influence of water on the formation mechanisms of 5-acetyl-3,4-dihydro-2H-1,4-thiazine

Abstract

The formation of 5-acetyl-3,4-dihydro-2H-1,4-thiazine in Maillard-type reactions of fructose with cysteamine under dry heating and cooking conditions was studied. Labelling experiments with 2-<sup>13</sup>C-fructose revealed, that the formation pathways are completely different, depending on the water content of the mixture. Under dry heating conditions, 5-(1-<sup>13</sup>C-acetyl)-3,4-dihydro-2H-1,4-thiazine is formed almost exclusively with the 2-<sup>13</sup>C of fructose found at the carbonyl carbon of the acetyl group. Under cooking conditions, ADHT is mostly unlabelled and most probably formed from erythrulose. Erythrulose might be generated from 2-<sup>13</sup>C-fructose by loss of 1-13C-acetic acid, indicated by the high amount of the latter found in the mixture. A possible mechanism leading from fructose to erythrulose is postulated.