Process for racemizing optically active .alpha.-amino acids or a salt thereof

A process for producing a DL-.alpha.-amino acid or a salt thereof which comprises racemizing an optically active .alpha.-amino acid or a salt thereof at a temperature of 20.degree. to 120.degree. C. in the presence of 2 to 50 g of an aliphatic acid per g of said optically active acid or salt, said aliphatic acid having the formula

• R.sup.1 --COOH (I)
• wherein R.sup.1 is hydrogen or alkyl having 1 to 4 carbon atoms, and 0.001 to 0.5 mole of an aldehyde per mole of said optically active acid or salt, said aldehyde having the formula:
• R.sup.2 --CHO (II)
• wherein R.sup.2 is hydrogen;
• alkyl having 1 to 6 carbon atoms;
• alkenyl having 2 to 4 carbon atoms;
• phenyl;
• phenyl having at least one substituent selected from the class consisting of hydroxy, nitro, amino and alkoxy having 1 to 4 carbon atoms;
• phenylvinyl;
• oxygen-containing heteromonocyclic group;
• and hydroxynaphthyl.