Liquid 2-hydroxy-4-methylthiobutyric acid and process for the preparation thereof

A process for the preparation of 2-hydroxy-4-methylthiobutyric acid having improved color, odor and lower viscosity, comprising the steps of

• hydrolyzing 2-hydroxy-4-methylthiobutyronitrile with sulfuric acid having an initial strength of betwen about 50% by weight and about 70% by weight on an organic-free basis, thereby producing an intermediate aqueous hydrolysis product solution containing 2-hydroxy-4-methylthiobutyramide;
• hydrolyzing said 2-hydroxy-4-methylthiobutyramide with sulfuric acid having a strength of between about 30% by weight and about 50% by weight on an organic-free basis, thereby producing an aqueous hydrolyzate solution containing 2-hydroxy-4-methylthiobutyric acid;
• contacting said hydrolyzate solution with a substantially water-immiscible organic solvent in a liquid/liquid extraction system to produce an extract comprising said solvent and 2-hydroxy-4-methylthiobutyric acid transferred from said hydrolyzate;
• and
• recovering said 2-hydroxy-4-methylthiobutyric acid from said extract in the presence of about 5% or more by weight water based on the amount of recovered 2-hydroxy-4-methylthiobutyric acid.