Formation of Sulfur-Containing Flavor Compounds from Reactions of Furaneol and Cysteine, Glutathione, Hydrogen Sulfide, and Alanine/Hydrogen Sulfide

Four reactions were carried out to compare the sulfur-containing compounds formed via Maillard reaction/Strecker degradation of cysteine with Furaneol and via the participation of hydrogen sulfide in the thermal degradation of Furaneol. GC−MS analysis showed that certain sulfur-containing compounds, such as 2,5-dimethylthiophene, 2,5-dimethyl-4-hydroxy-3(2H)-thiophenone, and 3,5-dimethyl-1,2,4-trithiolane were found in four reactions, while thiirane and 2-methylthiophene were only found in the Strecker degradation of cysteine and Furaneol. Furthermore, this study showed that the more sulfur-containing compounds were formed in the participation of hydrogen sulfide than in the Maillard reaction/Strecker degradation of glutathione and even cysteine, indicating that the availability of hydrogen sulfide in the reaction may be the limiting factor in the amount and the type of sulfur-containing compounds formed in the reactions. Cysteine and glutathione are used in the reaction because of the different states in which cysteine exists. The amino group of the cysteine residue in glutathione is peptide bonded and cannot participate in the Strecker degradation with a dicarbonyl compound. The amino group in the free cysteine molecule, however, is accessible to dicarbonyl compound and the Strecker degradation is possible. Therefore, the reaction mechanisms involved in the reaction between cysteine and Furaneol would be different from those in the reaction between glutathione and Furaneol. Keywords: Sulfur-containing flavor compounds; cysteine; glutathione; Strecker degradation; 2,5-dimethyl-4-hydroxy-3(2H)-furanone; hydrogen sulfide