Search

Chitosan (CS) is an excellent raw material for the preparation of food packaging films due to its good film-forming properties, non-toxicity, and biodegradability. However, pure chitosan films have drawbacks such as weak mechanical properties and limited antimicrobial activity. In this work, novel food packaging films containing chitosan, polyvinyl alcohol (PVA) and porous graphitic carbon nitride (g-C 3 N 4) were successfully prepared. The PVA served to improve the mechanical properties of the chitosan-based films, whilst the porous g-C 3 N 4 acted as a photocatalytically-active antibacterial agent. The tensile strength (TS) and elongation at break (EAB) of the g-C 3 N 4 /CS/PVA films both increased by ~4 times compared to the pristine CS/PVA films at the optimum g-C 3 N 4 loading of ~10 wt%. The addition of g-C 3 N 4 increase the water contact angle (WCA) of the films from 38° to 50°, whilst decreasing the water vapor permeability (WVP) from 160 × 10−12 to 135 × 10−12 g∙Pa−1 s−1 m−1. The shelf life of strawberries covered with g-C 3 N 4 /CS/PVA films at room temperature could be extended up to 96 h, compared to 48 h and 72 h for strawberries covered with polyethylene (PE) films or CS/PVA films, respectively. The g-C 3 N 4 /CS/PVA films offered good antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Further, the composite films could be easily recycled with the regenerated films offering almost identical mechanical properties and activities as the original films. The prepared g-C 3 N 4 /CS/PVA films thus offer promise for low-cost antimicrobial packaging applications. [Display omitted] • g-C 3 N 4 /CS/PVA photocatalytic packaging film was successfully prepared. • g-C 3 N 4 enhanced the barrier ability and antibacterial activity of the film. • PVA enhanced the mechanical properties and flexibility of the film. • The composite film showed better strawberries packaging properties. • The composite film can be easily recycled to prepare renewable film. [ABSTRACT FROM AUTHOR]

Cellulose acetate film, as a biodegradable and biomass-derived material, has great potential applications in food packaging. However, the poor mechanical and antibacterial properties limit its applications. Herein, a highly flexible carbon nitride-polyethylene glycol-cellulose acetate (CN-PEG-CA) film was successfully prepared by combining graphitic carbon nitride (g-C 3 N 4) photocatalyst with cellulose acetate (CA). The g-C 3 N 4 enables the film with antibacterial activity, as a green photocatalyst. PEG softens the rigid polymer CA and crosslinks CA, PEG, and g-C 3 N 4 together by hydrogen bonding, as a flexible crosslinker. X-ray diffractometer (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectrum (FT-IR) characterizations confirmed the successful preparation of the CN-PEG-CA film. The mechanical property tests demonstrated that adding PEG increased the elongation at break of the film by about 4 times. The composite film had high antibacterial activity, and the bactericidal rates on Escherichia coli and Staphylococcus aureus were 99.98 % and 99.89 %, respectively. It effectively extended the shelf life of strawberries to 96 h and effectively maintained the quality of strawberries during storage. After 96 h, the weight loss rate of strawberries packaged with 15 % CN-PEG-CA film was 21.83 %, vitamin C content was 45.47 %, titratable acidity content was 0.89 %, and color, hardness and total soluble solids were well maintained. And biocompatibility test results showed that the film was safe and nontoxic. From the ecological and economic point of view, the highly flexible and biodegradable films with efficient photocatalytic antibacterial activity synthesized in this paper have great potential in the field of food packaging. [Display omitted] [ABSTRACT FROM AUTHOR]