Three-Dimensional Printed Mulberry Anthocyanin Combined with Chitosan/Hydroxyethyl Cellulose Bilayer Films for Quality Preservation of Litchi

In this study, a bilayer antibacterial chromogenic material has been prepared using chitosan (CS) and hydroxyethyl cellulose (HEC) as the inner substrates, mulberry anthocyanins (MA) as natural tracers, and titanium dioxide nanoparticles (nano-TiO2) as bacteriostatic agent for the outer layer. By investigating its apparent viscosity and suitability for three-dimensional (3D) printing, the optimal ratio of the substrates was determined to be CS:HEC = 3:3 (CH). The CH viscosity was observed to be moderate. The printing process was consistent with no breakage or clogging, and the printed image was of high stability, and not susceptible to collapse and diffusion. Scanning electron microscopy and infrared spectroscopy indicated that the intermolecular binding between the substances exhibited good compatibility. Nano-TiO2 was evenly distributed in the CH, and no agglomeration occurred. The inner membrane fill rates affected the overall performance of the chromogenic material, with strong inhibitory effects against Escherichia coli and Staphylococcus aureus at different temperatures, as well as strong color stability. The experimental results indicated that the double-layer antibacterial chromogenic material can, to a certain extent, extend the shelf life of litchi fruit and determine the extent of its freshness. Therefore, from this study, we can infer that the research and development of intelligent materials have a certain reference value.