Novel antimicrobial biodegradable composite films as packaging materials based on shellac/chitosan, and ZnAl 2 O 4 or CuAl 2 O 4 spinel nanoparticles.

ZnAl ₂ O ₄ and CuAl ₂ O ₄ spinel nanoparticles were prepared by a modified Pechini method and used with the natural chitosan (CS) and shellac (SH) polymers to form novel composite membranes as promising food packaging materials. The selection of ZnAl ₂ O ₄ and CuAl ₂ O ₄  spinel nanoparticles was based on their antibacterial characteristics, availability, and economy. Using a straightforward and adaptable solution mixing and casting method, the bio-composites were created. The mechanical, physical, antibacterial, homogeneity and air permeability properties of composite films were investigated. The film structure was evaluated in terms of component interactions using FTIR spectra. The addition of 10% SH increased the tensile strength, percentage strain at maximum load, Young's modulus, and burst strength by 114-101%, 3.6-8.4, 103-119, and 179-153% for low and middle M.wt./CS respectively. Chitosan/shellac-CuAl ₂ O ₄  composite has superior properties compared to ZnAl ₂ O ₄  composite. In general, 0.05% spinel provides a composite having better qualities than that of 0.1 additions. Middle M.wt. chitosan provides a composite with superior properties compared to that of low M.wt. The incorporation of ZnAl ₂ O ₄ or CuAl ₂ O ₄ enhanced the thermal stability of the SH/CS composite. ZnAl ₂ O ₄ provides superior thermal stability than CuAl ₂ O ₄ . When shellac/CS film structure is treated with the previously indicated ZnAl ₂ O ₄ or CuAl ₂ O ₄ formulation, the % swelling decreases along with an increasing in the gel fraction. The antimicrobial assessment using inhibition zone diameter and shake flask methods showed that a composite of 1:9 shellac/chitosan/0.05% of CuAl ₂ O ₄ exerted the highest Gram-positive antibacterial activity against B. mycoides (21 mm), and C. albicans (22 mm). So, these enhancements make chitosan/shellac/ZnAl ₂ O ₄ or CuAl ₂ O ₄  composite films a good alternative to producing food packaging materials.
Competing Interests: Competing interests The authors declare no competing interests.
(© 2024. The Author(s).)