Hydrogen bond network-driven sustained-release antibacterial films of cinnamaldehyde microcapsules for the preservation of dried tofu.

Abstract

Soybean products rich in high-quality proteins have a short shelf life owing to their high water activity characteristics. In this study, sustained-release antibacterial composite films of cinnamaldehyde microcapsules (CAMs) were constructed for the preservation of dry tofu using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), and pullulan (PUL) as the composite matrix. CAMs with an encapsulation efficiency of 70.53% were prepared via complex coacervation using gelatin-Arabic gum as the wall material. Different contents of CAMs (0.5%, 1%, 2%, and 3% w/w) were added to the SHNC-film using the solution casting method. Fourier transform infrared spectroscopy and X-ray diffraction analysis confirmed that cinnamaldehyde was successfully embedded in the CAMs and crosslinked with the composite film matrix via hydrogen bonding to form a dense network structure. Scanning electron microscopy showed that the CAMs were well integrated into the composite film matrix without forming pores or cracks. Physical performance tests showed that after adding 2% (w/w) CAMs, the mechanical strength of the composite film was significantly improved (the tensile strength increased from 13.79 ± 1.67 MPa to 26.94 ± 2.02 MPa; P < 0.05), as were its hydrophobic properties (the contact angle increased from 25.7° ± 1.6° to 68.3° ± 1.6°), thermal stability, and ultraviolet barrier properties. The CAMs composite film (CAMs-film) significantly inhibited the proliferation of Pseudomonas fragi by inhibiting energy metabolism, degrading cell components and metabolic intermediates, and disrupting secondary metabolism (inhibition rate of 96.03%, P < 0.05). The composite film with 2% CAMs could extend the shelf life of dried tofu to 20 days at 4 °C. As a new environmentally friendly packaging material, the CAMs-film developed in this study can effectively extend the shel