Theoretical and experimental investigation of sodium alginate composite films containing star anise ethanol extract/hydroxypropyl-β-cyclodextrin inclusion complex.

The aim of this study is to prepare composite films incorporated with star anise ethanol extract (SAEE)/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex. The effects of sodium alginate concentration on mechanical properties of films are tested. Sodium alginate, SAEE, and SAEE/HP-β-CD inclusion complex-based composite films are characterized in terms of UV-visible spectroscopy, microstructure characterizations, including transmission electron microscopy, scanning electronic microscopy, Fourier transform infrared, and H NMR analysis, and molecular modeling calculations. With various stoichiometries, the complexes of sodium alginate/SAEE/HP-β-CD are compared through both theoretical and experimental analyses. Molecular simulations are applied to predict the possible orientations of SAEE inside the HP-β-CD cavity and the optimal stoichiometry of the complex formation. According to the simulation, the system of sodium alginate/SAEE (or SAEE/HP-β-CD inclusion complex) in a 3:1 stoichiometry reaches the lowest total energy and achieves a balance in complex system. In addition, the composite films can maintain high-content vitamin C and reduce weight loss rate of fresh-cut Chinese yam. In conclusion, coinciding with the experimental results, the molecular modeling successfully calculates the reasonable molecular structure and molecular behavior of sodium alginate/SAEE/HP-β-CD inclusion complex. The composite films in this study have the potential to be used for food packaging applications. PRACTICAL APPLICATION: In this paper, we present composite films incorporated with star anise ethanol extract (SAEE)/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complex for the use of fresh-cut Chinese yam preservation. The present study demonstrates a successful application of molecular modeling to predict the geometry of the final complex. It can serve as a powerful tool to calculate the energy of association between inclusion complex and sodium alginate molecules.