Effects of temperature-cycled retrogradation on properties of amylosucrase-treated waxy corn starch

Background and objectives: Though amylosucrase (AS)-treated starches have been studied recently, the retrogradation properties of AS-treated starches have not been studied yet. In this study, AS-treated waxy corn starch was retrograded by temperature cycling, and the effects of storage conditions on the structure and digestibility of the starch were investigated. Findings: Amylosucrase-treated waxy corn starch had a larger amount of long chains (degree of polymerization ≥25) than the control starch and exhibited amylose-like behavior. Temperature cycling induced the reassociation of the elongated chains of AS-treated starch and accelerated retrogradation, causing rapid and significant increases (p < 0.05) in melting enthalpy, relative crystallinity, and resistant starch (RS) content compared to those observed during isothermal storage. Conclusions: Structural changes affected the reassociation and/or melting properties of starch, as the two starches (control starch and AS-treated starch) had different favored steps of retrogradation (propagation and nucleation, respectively) during temperature-cycling storage. Significance and novelty: This study provided information on retrogradation-related changes in the properties of AS-treated starch. Temperature-cycled retrogradation can be used as a physical modification method to enhance the RS content of AS-treated starch, allowing AS-treated starch to be used as a low-glycemic index ingredient.