The persistence lengths for two different commercial starches were estimated from intrinsic viscosity measurements. The intrinsic viscosities of the starches were measured at 25 degrees C using 90/10 dimethy sulfoxide (DMSO)/water (weight/weight) as the solvent. The calculations were conducted using the equations developed by Yamakawa and Yoshizaki [Macromolecules 13, 633-633 (1980)] and corrected for polydispersity using the Schultz-Flory distribution. Values for the persistence lengths were 8.1 +/- 0.6 and 6.6 +/- 0.5 nm for a high-amylose potato, and a high-amylose maize starch, respectively. The values for the persistence length obtained for the two starch samples reflect the stiffness of the amylose chains in DMSO, which is due to the helical conformation of amylose in the solvent.