Preparation of chitosan/polyvinyl alcohol/white round grapefruit essential oil and polyethylene terephthalate films for Lycium barbarum preservation†

This study aimed to produce bilayer films spiked with white round grapefruit essential oil and apply them to preserve Lycium barbarum. A chitosan/polyvinyl alcohol film doped with white round grapefruit essential oil was prepared as an inner film, and a polyethylene terephthalate film was prepared as an outer film through a solution casting method. The volatile compounds of white round grapefruit essential oil (87.5573%), mainly D-limonene (34.389%), cis-p-mentha-2,8-dien-1-ol (5.154%), trans-carveol (5.148%), limonene oxide, cis-β-ocimene (4.892%) and trans-β-ocimene (4.130%), were identified through gas chromatography-mass spectrometry and found to have strong antimicrobial activities against Escherichia coli, Staphylococcus aureus, and Aspergillus niger. The addition of white round grapefruit essential oil to the chitosan/polyvinyl alcohol film resulted in a significant improvement in the flexibility and antimicrobial properties of the films; the thermomechanical properties were more stable; however, the film water content and soluble solid content changes were not significant. The double-layer film was applied in the preservation of Lycium barbarum, and results showed that the double-layer film effectively reduced the water loss rate, decay rate, malondialdehyde content, and color change of Lycium barbarum compared with the control group and prolonged the shelf-life of Lycium barbarum.