Fabrication and characterization of bioactive curdlan and sodium alginate films for enhancing the shelf life of Volvariella volvacea

This study aimed to develop bioactive films based on curdlan (CD) and sodium alginate (SA) to enhance the shelf life of the Volvariella volvacea mushroom. A stable nanoemulsion of droplet size of 150.1 ± 5 nm was first formulated using 5% soy protein (Sp) and 10% lavender essential oil (LEO), achieved by ultrasound treatment for 10 min, resulting in small droplet sizes. In parallel, a CD-SA film was prepared by mixing them in a 1:1 ratio. The SpLEO nanoemulsion was then ex situ added to the CD-SA film at varying concentrations (4%, 6%, 8%, and 10%). The resulting bioactive film exhibited desirable properties, including water vapor permeability (1.15 ± 0.05 × 10 −10  g m −1 Pa −1 s −1 ), swelling rate (547%), and tensile strength (10.1 ± 1.3 MPa). Docking and structural analyses suggested that ultrasound treatment enhanced the intermolecular hydrogen bonding, creating a uniform and regular surface and reduced crystallinity. The CD-SA film with ultrasound-treated 8% SpLEO nanoemulsion [i.e., (CD-SA/SpLEO-8)US] showed antibacterial activity against Escherichia coli and Staphylococcus aureus and extended the freshness of straw mushrooms prevention of spoilage during storage. Additionally, the film reduced respiration rate (975 mg CO₂/kg/h at 96 h) and ethylene production (160 ng/kg/s by 96 h) while effectively inhibiting straw mushroom autolysis. This led to a reduction in browning (2.91), total soluble solids (7.5%), weight loss (13.9%), and polyphenol oxidase activity (0.08 ΔOD 420 /min⋅g), thereby extending the shelf life of the mushrooms to 96 h. These findings highlight the potential of incorporating different molecules using ultrasound treatment to develop innovative edible films for food preservation.