The role of entanglement concentration on the hydrodynamic properties of potato and sweet potato starches

The hydrodynamic properties of potato starch and sweet potato starch in dilute and semi-dilute aqueous solutions were studied using a Ubbelohde viscometer, a transmission electron microscope, and steady shear rheological measurements. The results indicated that the potato starch solutions showed a linear shape of the ηred versus c curves. The sweet potato starch solutions presented a non-linear shape with a downturn in dilute solutions, or the concentrations were lower than entanglement concentration (ce). The ce values of the potato and sweet potato starch solutions were 0.43% and 0.54%, respectively. These findings indicated that the impact of the ce value on the network formation of the potato starch solutions was much more significant compared with the impact on the sweet potato starch solutions. The potato and sweet potato starch solutions showed shear thinning behaviour hardly occurs when the concentrations were less than ce, while shear thinning behaviour approached when the concentrations were equal to or greater than ce. Similarly, the potato and sweet potato starch solutions rarely resembled a pseudoplastic state when the concentrations were lower than or equal to ce, while the pseudoplastic behaviour developed when the concentrations were higher than ce.