Influence of Cysteine Oxidation on Thermal Formation of Maillard Aromas

Cysteic acid and cysteinesulfinic acid, which are oxidized forms of reduced cysteine, were heated separately with d -glucose in an aqueous system of pH 6 at 160 °C for 2 h. The reaction products were extracted and analyzed. Among the identified compounds, pyrazines and furans are the most predominant compounds and no or only trace amounts of sulfur-containing compounds were identified in these two reaction systems. In the same reaction condition, the reduced cysteine and d -glucose produced mainly sulfur-containing compounds; no pyrazines were found in this system. The reaction mass of cysteic acid and d -glucose possessed smoky, nutty, and yeasty aromas, while cysteinesulfinic acid with d -glucose generated a strong coffee note. The reduced cysteine with glucose produced onion and garlic, as well as slightly meaty and sulfury, flavors.