The present study aims to develop nanofiber mats via the electrospinning technique by using Dillenia indica mucilage (DIM) as a new source of hydrocolloid, polyvinyl alcohol (PVA), and biosynthesized zinc oxide nanoparticles (ZnO NPs). Dillenia indica, an underutilized fruit within the Dillenia genus, widely distributed in South and Southeast Asian countries. This fruit contains gelatinous pulp (around 10%) covered with hard imbricate sepals with no commercial utility, used as a single sustainable source for both mucilage (extracted from the gelatinous pulp) and ZnO NPs (biosynthesized using sepals extract). Different volume ratios (100:0, 90:10, 80:20, 70:30, 60:40,50:50 and 0:100) of PVA (8% w/v) was blended with the DIM (1% w/v) solution to formulate the PVA–DIM spinning solutions. Further, various concentrations of ZnO NPs (0.1%, 0.3% and 0.5% w/v) were added to the selected volume ratio of PVA and DIM solution. The proximate composition of extracted mucilage powder revealed the contents of moisture (9.96 %), ash (7.84 %), protein (5.84 %), fat (0.08 %) and carbohydrate (36.64 %). Steady shear measurements at different concentrations of mucilage aqueous solutions (1, 2 and 3 % w/v) exhibited shear thinning behaviour. Further, frequency sweep experiments indicated the dominance of storage modulus(G′) than loss modulus (G″) at mucilage concentrations (2 % and 3 %), suggesting weak gel formation capability. The size of synthesized ZnO NPs was varied from 40 nm to 120 nm with the average particle size of 70.2 nm. The viscosity and electrical conductivity of PVA / DIM spinning solutions with different volume ratios (100:0, 90:10, 80:20, 70:30, 60:40, 50:50 and 0:100) were in the range of 181–74 m.Pa.s and 395 –1660.66 µs/cm, respectively. The morphology of nanofibers was investigated using field emission scanning electron microscopy (FESEM) that showed an average diameter range of 173.72 –133.52 nm. The development of electrospun nanofiber mats with maximum blending of 8% PVA with 1% DIM in a 60:40 ratio allowed successful fabrication of stable nanofiber mats. The added ZnO NPs at varied concentrations (0.1%, 0.3%, 0.5%) to the above volume ratio, improved both the antimicrobial and mechanical performance of the mats. The optimal loading of 0.3% ZnO NPs achieved a tensile strength of 18.03 ± 0.50 MPa and water vapor permeability of 18.23 ± 0.74 (g·mm)/(m²·day·KPa). These nanofiber mats demonstrated effective antibacterial activity against both E. coli and S. aureus. The resulting nanofiber mats have a potential for active food packaging applications. Further, Integration of pH-sensitive anthocyanins into these mats enabled real-time food monitoring, adding an intelligent functionality.

Keywords: Mucilage, Rheology, Electrospinning, ZnO nanoparticles, Active packaging