Long-term low shear-induced highly viscous waxy potato starch gel formed through intermolecular double helices

We previously reported that waxy potato and corn starch amylopectin pastes undergo a shear-thickening behavior that occurs at a low shear rate range of 5 to 25 s^-1, and that the effect did not occur for waxy rice starch. Here, we show that the same gelatinized potato amylopectin subjected to a prolonged shear rate of 20 s^-1 for 24 h at 5 °C forms a highly viscous gel having a 4-fold higher number of double helices than without shear. Shear-induced starch retrograded aggregates began forming within 20 min of treatment. Amylopectin double helices melted between 40-75 °C resulting in a steep decrease in the storage modulus, indicating that gel formation was caused by intermolecular double helices. Thus, a new phenomenon is reported whereby a waxy potato amylopectin paste, in the presence of long-term low shear, forms double-helical aggregated structures that considerably affects the material's rheological properties.