Toward sustainable postharvest management: A fully bio-based and multifunctional film for fruit preservation

In response to the decline in fruit quality post-harvest caused by intense metabolism, microbial infections, and nutrient depletion, this study has successfully developed a multifunctional composite film (SPP16-TE). This film boasts UV-blocking, antibacterial, antioxidant, and biodegradable properties. The film was fabricated using sodium alginate (SA) and polyvinyl alcohol (PVA) as fully biodegradable matrices, together with the natural cross-linker phytic acid (PA) and anthocyanin-rich Zijuan tea extract (TE) as sustainable functional agents. Results show that the addition of PA significantly enhanced film flexibility (EAB: SP=30.54%, SPP16=103.32%), UV-blocking capability (SE%: SP<80%, SPP16=80-95%), and soil degradation rate (SP=30.74%, SPP16=81.23%). Mechanistically, the cross-linking effect of PA strengthened the polymeric network, improving ductility, while its light-absorbing properties contributed to UV shielding. The accelerated degradation is attributed to the acidic hydrolysis facilitated by PA. In comparison, the integration of TE imparted excellent antioxidant properties (with ABTS and DPPH radical scavenging rates of 96.71% and 96.05%, respectively) and antibacterial activity (exhibiting inhibition rates of 11.29% and 33.00% against Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus , respectively). These functionalities are ascribed to the anthocyanins and polyphenols in TE, which can donate hydrogen/electrons to neutralize free radicals and disrupt microbial cell membranes. In the fresh application of blueberries and green grapes, this film effectively slowed the loss of fruit weight, the decrease in hardness, and the deterioration of appearance quality, likely by establishing a modified atmosphere, reducing oxidation, and suppressing microbial growth. This work proposes a green and scalable strategy for sustainable fruit and vegetable preservation.