Improved properties of potato starch/myristic acid composite films via high hydrostatic pressure: the role of pressure-induced intermolecular interaction

In this study, an innovative approach was proposed to prepare potato starch/myristic acid composite film using a high hydrostatic pressure (HHP) process to improve its properties. The myristic acid/potato starch ratio in the composite films significantly increased after HHP treatment, resulting in substantial improvements in the physicochemical properties of the films. HHP-treated film presented a more uniform and smooth surface morphology, whereas the tensile strength was significantly improved. Meanwhile, water vapor permeability, water solubility, and moisture content decreased altogether. Most importantly, HHP treatments substantially enhanced the hydrophobicity of the composite film as the water contact angle increased from 33.2% to 46.2%. Raman spectroscopy and FT-IR results confirmed that HHP altered the intermolecular interaction between potato starch and myristic acid, forming more hydrogen bonds with shorter bond lengths. It led to the structural transformation from V6I complexes to V6II and V6III complexes, with relative crystallinity increased from 35.46% to 44.56%. This work provided a novel pressure-assisted method to fabricate starch/lipid biopolymer film with substantially improved hydrophobicity, thermal stability, and mechanical properties.