Breathable and Washable Pullulan-Based Nanofiber Films for Visual Monitoring and Antibacterial Fruit Preservation

Maintaining the freshness of fruit is a critical goal for the industry and consumers, yet it remains challenging due to postharvest spoilage and a lack of real-time freshness-monitoring capacity. Herein, a series of breathable and washable nanofiber films have been developed for effective and multifunctional fruit preservation. The pullulan-based nanofiber films incorporating anthocyanin (An) and quaternized chitosan (HACC) are fabricated via an electrospinning process using water as the sole solvent. Using An as the antioxidant and pH-monitoring component, the nanofibers exhibit strong free radical scavenging and color response from purple-red to green over a wide pH range from 2.0 to 12.0, showing the potential for pH-responsive freshness indication. The 2.5 wt % HACC sample confers antibacterial capacity, with inhibition zones (16.5 and 14.9 mm) and antibacterial rates (98.91% and 99.94%) for E. coli and S. aureus, respectively. Compared to polyethylene film, they exhibit superior breathability, which helps mitigate moisture condensation and suppress mold proliferation. Fruit preservation experiments using either film covering or in situ electrospinning confirm its antibacterial activity, freshness indication, and water washability (10 s), extending the shelf life by over 60% compared to the control group. This work offers an eco-friendly strategy for multifunctional packaging.