A novel active packaging film containing citronella oil: Preparation, characterization, antimicrobial activity and application in grape preservation

In this study, citronella oil (CO) was incorporated into soy protein isolate (SPI) to prepare antimicrobial protein films capable of inhibiting the growth of spoilage microorganisms on food packaging and providing effective preservation of food products. The morphological, physical and functional properties of the antimicrobial protein films were characterized and investigated by different characterization tools. The SEM results showed that the surface of the films was relatively smooth and flat. FTIR and XRD analyses indicated that CO was uniformly distributed in SPI with good compatibility. Under UV light, the films containing CO showed moderate light transmission and better UV-blocking properties than the SPI-based films. The addition of CO improves the hydrophobic property of the films, and the water content of the film containing 3 % CO is reduced to 20 % compared with that of the SPI film with 27.5 %. The DMA showed that the prepared films had good tensile, swelling and relaxation properties. Antimicrobial protein films containing 3 % CO showed high antimicrobial activity against S. aureus and E. coli. It was also found that the film with 3 % CO had a survival rate of more than 70 % and an apoptosis rate of 5.3 % for BEAS-2B cells after 48 h, indicating that such films are safe. Moreover, the film with 3 % CO showed good freshness and storage capacity with a weight loss of 44.16 % after the grapes had been packed for 7 days. These good physical properties and functional properties suggest that films containing CO have great potential for food packaging applications.