Developing high-strength, multifunctional films from tamarind seed polysaccharides and propolis for sustainable fruit preservation

Fiber-reinforced tamarind seed polysaccharide-starch film has high tensile strength. • Propolis enables UV-barrier, antioxidant and antibacterial functions (>97%). • Extends fruit shelf life, exhibits soil biodegradability and clean combustion. Developing sustainable food packaging that integrates structural integrity with active functionality remains a central challenge for next-generation biopolymer materials. This study presents a hierarchical design strategy to fabricate a high-performance tamarind seed polysaccharide (TSP) based composite film, wherein natural seed fibers provide macroscopic reinforcement and propolis extract (PE) serves as a molecular-scale active modulator. Despite the inclusion of starch, the fiber-containing tamarind gum/pre-gelatinized starch/propolis extract composite films (TPP-0%) maintained a high tensile strength of 27.51 ± 0.97 MPa, comparable to that of pure TSP film (27.31 ± 1.19 MPa). Multiscale structural analysis reveals that PE induces a densified amorphous matrix and a dynamically reconfigured hydrogen-bond network, which collectively balance mechanical robustness and flexibility. The films demonstrate superior barrier properties against water vapor and UV radiation, alongside potent antioxidant and broad-spectrum antibacterial activity (>97% against E. coli and S. aureus ). Practical preservation tests confirm their efficacy in extending the shelf life of fruits by mitigating oxidative browning and microbial proliferation. Coupled with favorable soil biodegradability and clean combustion behavior, this work establishes a scalable and eco-friendly paradigm for structurally integrated, multifunctional food packaging.