Time-temperature-dependent structuring of corn starch biopolymer films under retrogradation conditions

This study explores the structural evolution of corn starch-based films fabricated via the casting method under various thermal conditions and retrogradation times. Emphasis was placed on the molecular organization of the amylose and amylopectin chains. At a fixed retrogradation duration, increasing the processing temperature resulted in a progressive decline in the CC bond density, amylose content, crystallinity, molecular order, and double helix formation. Additionally, the chain length distribution (CLD) shifted from longer B1 chains toward shorter A chains, and the polydispersity index (PDI) increased with increasing temperature. In contrast, under constant-temperature conditions, extending the retrogradation time led to increases in the CC bond content, amylose proportion, and overall molecular order and crystallinity. Over time, the A chain content and the PDI decreased, whereas the B1 chains became more prominent. These insights advance the understanding of starch retrogradation mechanisms, contributing to the design of biobased films with tunable structural properties and supporting innovations in biodegradable packaging and resource-efficient material development.