Patent ID: 8119837

Claim:
A process for producing a methionine comprising the following steps (1) to (3), wherein the content of thiols in 3-methylthiopropanal is 500 ppm or less, based on the propanal, and the content of hydrogen sulfide in 3-methylthiopropanal is 60 ppm or less, based on the propanal; step (1) in which 3-methylthiopropanal is reacted with hydrogen cyanide in the presence of a base to give 2-hydroxy-4-methylthiobutanenitrile; step (2) in which the 2-hydroxy-4-methylthiobutanenitrile obtained in step (1) is reacted with ammonium carbonate to give 5-(β-methylmercaptoethyl)hydantoin; and step (3) in which the 5-(β-methylmercaptoethy)hydantoin obtained in step (2) is hydrolyzed in the presence of a basic potassium compound to give methionine.