Starch retrogradation, colloidal dynamics, and digestibility mechanisms in nixtamalized maize tortillas

abstract

This study provides a mechanistic understanding of how refrigerated storage affects the starch structure, colloidal dynamics, and digestibility of tortillas prepared from nine commercial nixtamalized maize flours that differ in pigmentation and processing history. Multiscale analyses, including thermal and crystalline transitions (DSC/XRD), molecular architecture (HPSEC-MALLS, HPAEC-PAD), colloidal behavior (zeta potential, particle size), texture, and in vitro digestion were integrated to elucidate structure-function relationships during 0¿168 h of storage at 4 °C. Cold storage progressively increased gelatinization enthalpy (¿H + 2¿3 J g¿1) and relative crystallinity (+3¿5 %), driven by amylopectin. These structural reorganizations shifted starch fractions toward higher resistant starch (RS + 8¿12 %) and slightly reduced the predicted glycemic index (¿3 to ¿7 units). Blue maize tortillas, enriched in polyphenols, exhibited weaker crystallinity and slower retrogradation yet achieved lower initial RDS and pGI, consistent with starch-polyphenol interactions that hinder enzymatic access. Particle size and zeta potential kinetics revealed that retrogradation generates steric and electrostatic barriers to ¿-amylase hydrolysis, providing a mechanistic link between molecular order and digestibility. A multivariate ranking that integrates starch structure, textural integrity, and digestibility identified flour-storage combinations that optimize a low glycemic response without compromising pliability. These findings reveal the molecular and colloidal mechanisms governing cold-induced starch reorganization in tortillas, offering practical strategies to design maize-based foods with improved metabolic functionality and controlled staling. © 2025 Elsevier Ltd.