Long-term low shear of a waxy potato starch paste produces a highly viscous gel by formation of intermolecular double-helices.

Our group recently reported that waxy potato and corn pure starch amylopectin pastes undergo a shear-thickening behavior at a low shear rate range of 5 to 25 s$^{\mathrm{-1}}$, and that the effect did not occur in waxy rice starch. Here, we show that gelatinized potato amylopectin subjected to prolonged shear at 20 s$^{\mathrm{-1\thinspace }}$for 24 h at 5$^{\mathrm{o}}$C produced a highly viscous gel with 5x more double-helices than without shear. Shear-induced aggregates formed within 20 min. Double-helices melted between 40 to 75$^{\mathrm{o}}$C leading to a total loss of gel elasticity and a steep decrease in G', indicating that the retrogradation process occurred in part among amylopectin molecules (i.e. intermolecularly). Thus, a new phenomenon is reported whereby waxy potato amylopectin with long linear chains forms double-helical aggregated structures in the presence of long-term low shear that dramatically affects material properties.