Polymorphic Control of α and β dl‐Methionine through Swift Cooling Crystallization Process

Polymorphic control and crystal nucleation of α and β polymorphs of dl‐methionine, an essential amino‐acid, is attained from saturated aqueous solution through swift cooling crystallization process by generating wide range of supersaturation (0.02 < σ < 2.19) in the temperature range of 323–274 K. The type of nucleation is very much supersaturation dependent: while lower supersaturation range (0.02 < σ < 0.08) prefers the stable β form, higher supersaturation range (1.20 < σ < 2.19) yields metastable α form. In situ optical microscopy and X‐ray diffraction analyses confirm the morphological and structural distinction of the grown polymorphs.