A Rapid and Precise Method to Determine Cysteine Content in Food Materials using 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole

A method to determine cysteine content in food materials using 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxidiazole (ABD-F) was compared to a method using N-acridinyl maleimide (NAM). Cysteine in samples was derivatized with two fluorogenic reagents and analyzed using HPLC. The cysteine derivative with ABD-F gave a single peak while the cysteine derivative with NAM produced three peaks in standard. The cysteine content in model samples determined with ABD-F was nearly identical to the content determined with NAM. However, when the cysteine content of six types of food materials was measured, four samples were identical in each method, but two samples produced different results because the separation of cysteine derivatives with NAM was influenced by other compounds in the food samples. Since the ABD-F method gave the better separation, it can be useful for the determination of cysteine content in food materials.