Studies on the Formation and Stability of the Roast-Flavor Compound 2-Acetyl-2-thiazoline

2-(1-Hydroxyethyl)-4,5-dihydrothiazole (HDT) was identified by ¹H- and ¹³C-NMR measurements as the main volatile product formed by storage of an aqueous solution of cysteamine and methylglyoxal at low temperatures (6 °C). The structure of HDT was confirmed by synthesis. Systematic studies on the thermal stability of the HDT under different conditions either in aqueous solution or during high-resolution gas chromatography revealed that HDT is an important intermediate in the formation of the intensely roasty smelling food flavor compound 2-acetyl-2-thiazoline (AT). Model studies showed that more than 10% of the precursor HDT was converted into AT simply by heating for 10 min in water. The activation energy of this reaction was 57.4 kJ/mol. Experiments on the thermal stability of AT itself revealed that heating in aqueous solution also led to a degradation of AT, whereas heating in an oil significantly stabilized the flavor compound.