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

This study aimed to produce bilayer films spiked with white round grapefruit essential oil and apply them to preserve <i>Lycium barbarum</i>. 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%), <i>cis-p</i>-mentha-2,8-dien-1-ol (5.154%), <i>trans</i>-carveol (5.148%), limonene oxide, <i>cis</i>-β-ocimene (4.892%) and <i>trans</i>-β-ocimene (4.130%), were identified through gas chromatography-mass spectrometry and found to have strong antimicrobial activities against <i>Escherichia coli</i>, <i>Staphylococcus aureus</i>, and <i>Aspergillus niger</i>. 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 <i>Lycium barbarum</i>, and results showed that the double-layer film effectively reduced the water loss rate, decay rate, malondialdehyde content, and color change of <i>Lycium barbarum</i> compared with the control group and prolonged the shelf-life of <i>Lycium barbarum</i>.