Response surface optimization and characterization of PVA–Gelatine nanofibers loaded Syzygium polyanthum (Wight) Walpers extract for active strawberry packaging

Syzygium polyanthum (Wight) Walpers, known as Indonesian bay leaf, is an Indonesian medicinal plant rich in bioactive compounds with potential antibacterial properties. The demand for sustainable food packaging and the rapid spoilage of strawberries have prompted the development of biodegradable active packaging materials with antibacterial properties. This study aimed to optimize and characterize electrospun polyvinyl alcohol–Gelatine (PVA/Gelatine) nanofibers loaded with Syzygium polyanthum (Wight) Walpers Extract (SPE) for active strawberry packaging. The electrospinning parameters were optimized using response surface methodology-central composite design (RSM–CCD) by evaluating the effects of applied voltage (8–16 kV) and tip-to-collector distance (80–200 mm) on the nanofiber diameter. The quadratic model showed high significance, with an F-value of 242.7 and p < 0.0001. Optimum electrospinning was achieved at 14.98 kV and 176.30 mm, producing a predicted nanofiber diameter of 223.692 nm with a desirability value of 1.000. SEM analysis revealed smooth, continuous, and bead-free nanofibers with average diameters increasing from 180.66 ± 32.52 nm for PVA/gelatin to 222.85 ± 34.34 nm after SPE incorporation. Mechanical characterization demonstrated improvements in Young’s modulus from 169.39 ± 10.23 MPa to 389.21 ± 10.55 MPa and tensile strength from 39.25 ± 1.23 MPa to 51.22 ± 1.45 MPa, while the elongation at break decreased from 22.58 ± 2.36% to 13.19 ± 2.98%. Wettability analysis showed an increase in the water contact angle from 94.95° ± 3.21 to 103.05° ± 4.75 °and a reduction in water absorption from 170% to 132% after 60 min of immersion. FTIR and XRD confirmed the incorporation of SPE and intermolecular hydrogen bonding. The nanofibers exhibited antibacterial activity against S. aureus (8–11 mm) and E. coli (6–9 mm) and delayed strawberry spoilage for up to 8 days. These results demonstrate the potential of these nanocomposites as sustainable active packaging materials for the preservation of fresh fruits.