Fabrication and characterization of Plumula nelumbinis extract loaded gelatin/zein films (PNE@GZF) to prolong strawberries shelf-life

The encapsulation of natural-derived antimicrobial materials within packaging films is a promising strategy for food preservation. Nevertheless, such materials often exhibit inadequate inhibitory capabilities against both bacteria and fungi. In this work, an extract (phenol alkaloids) obtained from the green embryos of lotus seeds (Plumula nelumbinis, PNE) was encapsulated into the gelatin/zein films (GZFs), which was designed to extend the shelf-life of strawberries. The GZFs varied with different zein ratios (1%, 5%, and 9%) were fabricated by the solvent casting method. GZF5, which containted 5%wt. zein, was selected as the optimal film matrix for loading PNE at various concentration (0.8, 1.6, 3.2 mg/mL), due to its desired transparency, highest water contact angle of 77.30 ± 3.52°, minimized water evaporation rate of 9.50 ± 1.99%, and favorable oxygen barrier properties of 0.92 ± 0.06 cc/m·24 h atm. Notably, the loaded PNE demonstrated the ability to inhibit the growth of gram-positive bacteria (Staphylococcus aureus), gram-negative bacteria (Escherichia coli) and various fungi (Botrytis cinerea, Aspergillus Alternaria and Aspergillus terreus) even at a concentration as low as 1.6 mg/mL. Furthermore, PNE exhibited robust antioxidant activity at 0.8 mg/mL. As a result, the strawberries coated with PNE0.8@GZF5 (0.8 mg/mL PNE) exhibited complete preservation, when challenged with 1 × 106 CFU of Botrytis cinerea. This study highlights the potential of PNE-incorporated edible film as an innovative and practical packaging material for effective postharvest microbial control.