Spherulitic crystallization of aspartame from aqueous solution in a two-dimensional cell

Abstract An artificial sweetener, aspartame (α-L-aspartyl-L-phenylalanine methyl aster) was crystallized as spherulites in the order of magnitude of centimeters in radius. With increasing relative supersaturation σ, the number of nucleation sites increased, but the radius of the largest spherulite in the cell decreased. The growth rate G of the spherulite was 1–2 mm/min and is given as a function of σ by the experimental equation: G = 8.45 x 10 -2 σ 1.95 . Individual fiber crystals of the spherulite grew slowly in the diameter direction until a critical diameter (10 μm or so) was attained. Longitudinally, however, they grew fast. They repeatedly split and branched during growth, spreading radially to form spherulites.