Stored Gelatinized Waxy Potato Starch Forms a Strong Retrograded Gel at Low pH with the Formation of Intermolecular Double Helices

Waxy potato amylopectin has longer internal and external linear chains than rice or corn amylopectin that are capable of retrograding to a higher degree, but its molecular recrystallization is impeded by unprotonated phosphate groups. Here, we studied whether retrogradation and gel properties of waxy potato starch can be enhanced by lowering pH. The gel strength of waxy potato starch was strongly inversely correlated with pH, going from 10 to 4, and its magnitude was higher at pH values in which the ζ potential of the system was low. Waxy potato starch formed a strong aggregate gel driven by the formation of intermolecular double helices (G′ drop25–95 °C ≈ 1358 Pa, melting ΔH = 9.5 J/g) when conditions that reduce electrostatic repulsion (pH 4, ζ = −1.7) are used, a phenomenon that was not observed in low-phosphorylated waxy cereal starches (i.e., waxy rice and corn).