Polyethylene/Hydrophobic Calcium Lignosulfonate Composite Film for Anti-Photooxidation of Fuji Apples

Excessive ultraviolet (UV) radiation exposure induces photooxidative stress in plants, leading to severe cell damage. Current packaging films often rely on nonrenewable, petroleum-based UV absorbers, which may pose potential health risks. Calcium lignosulfonate, a natural byproduct derived from the pulp and paper industry, has attracted significant attention as a sustainable alternative to petroleum-based UV absorbers. In this study, calcium lignosulfonate was hydrophobically modified to enhance its compatibility with nonpolar low-density polyethylene (LDPE), and a UV-blocking composite film was subsequently fabricated. The hydrophobic modification significantly increased the water contact angle of calcium lignosulfonate from 5° to 101°. Incorporating the modified calcium lignosulfonate into LDPE improved both the melting point and crystallinity of the polymer. The resulting composite film demonstrated excellent UV-blocking performance, achieving a UV-A blocking rate of 95% and a UV-B blocking rate of 99%, and effectively mitigated photooxidative browning in “Fuji” apples. This film exhibits great potential for anti-photooxidation packaging applications while simultaneously reducing dependence on petroleum-based resources.