Abstract: A process by which high-quality crystals of methionine in the form of granules or thick plates having high bulk density can be stably produced. The process for production of methionine comprises the step of hydrolyzing 5-(2-methylmercaptoethyl)hydantoin into a metal salt of methionine by the use of at least one metal compound selected from the group consisting of metal hydroxides, metal carbonates, and metal bicarbonates, the step of neutralizing the metal salt of methionine under pressurizing with carbon dioxide to crystallize methionine, the step of separating the resulting mixture into methionine and a filtrate, and the step of recycling the filtrate to the step of hydrolysis of 5-(2-methylmercaptoethyl)-hydantoin, wherein the content of methionine polymers and/or salts thereof in the aqueous solution used in the crystallization step in terms of methionine polymers is adjusted to 8 wt % or below based on the amount of methionine to be formed.

Abstract: A process by which high-quality crystals of methionine in the form of granules or thick plates having high bulk density can be stably produced. The process for production of methionine comprises the step of hydrolyzing 5-(2-methylmercaptoethyl)hydantoin into a metal salt of methionine by the use of at least one metal compound selected from the group consisting of metal hydroxides, metal carbonates, and metal bicarbonates, the step of neutralizing the metal salt of methionine under pressurizing with carbon dioxide to crystallize methionine, the step of separating the resulting mixture into methionine and a filtrate, and the step of recycling the filtrate to the step of hydrolysis of 5-(2-methylmercaptoethyl)-hydantoin, wherein the content of methionine polymers and/or salts thereof in the aqueous solution used in the crystallization step in terms of methionine polymers is adjusted to 8 wt % or below based on the amount of methionine to be formed.