Effect of Cysteine Addition on the Volatile Compounds Released at the Die during Twin-screw Extrusion of Wheat Flour

Numerous sulfur-containing volatile compounds were released from an extruder when cysteine was added to wheat flour before extrusion. The volatiles released were collected in a specially designed cryogenic apparatus at the die of the twin-screw extruder. Five concentrations of cysteine were used (0 to 10 g/kg). Among the identified sulfur-containing compounds, meat-like flavor compounds, such as 2,4-dimethyl-3-thiazoline, 2-methylthiazolidine, 3,5-dimethyl-1,2,4-trithiolane, and 2,4,6-trimethyl-perhydro-1,3,5-dithiazine, were collected in the highest amounts. Several nonsulfur containing compounds such as methylpyrazine, 2,6-dimethylpyrazine, and 2-acetyl furan were also found in the condensate. The total amount of volatiles collected increased when more cysteine was added to the flour, but only a small fraction of added cysteine formed flavor volatiles in both the condensate and extrudate.