Biosynthesized metal nanoparticles from agro-industrial byproducts applied in the functionalization of bioplastics for use in the blueberry packaging

In this study, silver (Ag), zinc oxide (ZnO), and silicon dioxide (SiO₂) nanoparticles (NPs) were synthesized using phenolic compound-rich extracts from agro-industrial by-products of blueberries and asparagus. The NPs exhibited average sizes of 3.07 ± 2.38 nm (Ag), 70.42 ± 18 nm (ZnO), and 104.38 ± 11.7 nm (SiO₂) with high colloidal stability (Z potentials: −35.63 mV for Ag, −33.9 mV for ZnO, and −10 mV for SiO₂). Bioplastics functionalized with these NPs showed improved properties: increased rigidity (Young's modulus up to 2690 MPa in B–SiO₂), reduced water absorption (160.64 g/100 g dry matter in B–Ag), high transparency (87.87 % in B-Control, 87.83 % in B–ZnO), and lower wettability (contact angle of 102.4° in B–ZnO). Thermal stability also improved, with B–SiO₂ exhibiting the lowest mass loss (31.12 %) in TGA. Bioplastics with Ag demonstrated strong antimicrobial activity, maintaining low mold and yeast counts (<10 CFU/g). Biodegradation was faster in soil than in marine environments, with NPs modulating rates. As primary and secondary packaging for blueberries, Ag-functionalized bioplastics reduced mass loss and preserved firmness for up to 56 days at 4.3 °C, with no NP migration detected by XRF and FTIR. This research highlights a sustainable approach using agro-industrial by-products to develop functional bioplastics, aligning with circular economy principles and reducing environmental impact in the food packaging sector.