Effects of enzymatically interesterified plastic fat on starch structure and digestibility in frozen cooked noodles

Starch in frozen cooked noodles (FCNs) is prone to retrogradation during storage, causing textural and sensory deterioration. This study investigated the effects of enzymatically interesterified soybean oil-based plastic fat (EIPF) on starch structure, retrogradation, and digestibility in FCNs. EIPF significantly increased gelatinization temperatures (T o , T p , T c ), enthalpy (ΔH), and relative crystallinity (P < 0.05), indicating delayed gelatinization and enhanced thermal stability. It also reduced the I 1045 /I 1022 ratio and enhanced starch-iodine binding, suggesting inhibited chain reassociation and mitigated retrogradation. Confocal laser scanning microscopy showed that EIPF significantly preserved starch granule integrity, maintaining 77.43% intact regions after 12 weeks compared with 63.97% in the control (P < 0.05). Additionally, EIPF significantly lowered rapidly digestible starch (RDS), increased resistant starch (RS) by 11.95% (P < 0.05), and slowed starch hydrolysis. This effect is likely due to steric hindrance and reduced enzyme accessibility. The formation of ordered starch–lipid structures may reduce enzyme accessibility to starch chains and slow starch hydrolysis. Overall, EIPF formed stable supramolecular structures with starch, increasing crystallinity and thermal resistance, suppressing retrogradation, and reducing digestibility. These findings provide new insights into the application of functional lipids for improving the quality and nutritional characteristics of FCNs.