Multi-scale structural influence of starch on their interaction of caffeic acid and starch after freeze-thaw: Taking potato starch and lotus seed starch as examples.

Interactions between polyphenols and starch affect the quality of starch-based products. In this study, we investigated the interaction between caffeic acid (CA) and starches with different structures (lotus seed starch (LSS) and potato starch (PS)) after freeze-thaw, and the effects of CA on the physicochemical properties of starch. The results show that CA has distinct effects on starch, driven by differences in the multiscale structure. LSS exhibited a stronger binding capacity to CA based on complexing index and iodine binding analysis. Hydrogen bonding was identified as the primary driving force between CA and starch chains of LSS and PS supported by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). After addition of CA, the thermodynamic parameters and swelling power of LSS increased, whereas those of PS decreased, which was attributed to variations in the interactions between the -OH groups of CA and amylopectin/amylose through hydrogen bonding. Rheological, textural, and microstructural analyses revealed that CA decreased the viscoelasticity, gelation ability, textural characteristics of both starch gels, and disrupted the starch gel network, with LSS being the most affected. This study provides a theoretical basis for adjusting the quality of frozen starch-based foods based on the interactions between polyphenols and starch.