A Readily Degradable Polyvinyl Alcohol/Starch Membrane Containing Catechol-Grafted Microcrystalline Cellulose for Preserving Fruit Freshness.

Copolymer membranes based on polyvinyl alcohol (PVA) and starch suffer from low mechanical strength and poor fresh-produce preservation and degradation performance. Adding functional cellulose or derivatives to membranes can improve these properties. Herein, free radical grafting polymerization between microcrystalline cellulose (MCC) and catechol (CA) was performed using a horseradish peroxidase (HRP)/acetylacetone/H₂O₂ system, and the product was incorporated into a PVA/Starch membrane to improve its performance. The MCC-CA polymer was structurally characterized by FTIR, ¹H NMR, ¹³C NMR, XRD, and HPLC methods. The covalent binding mechanism during the free radical polymerization process was analyzed and optimized based on HRP enzyme dosage, H₂O₂ dosage, CA dosage, reaction temperature, and reaction duration. The mechanical properties, antioxidant properties, degradation properties, and freshness properties of the Starch/MCC-CA membrane were explored. The results indicated MCC and CA were graft polymers between free radicals; the Starch/MCC-CA membrane had a significant improvement in degradation, free radical scavenging properties, and mechanical properties, with the freshness of bananas maintained for > 10 days, superior to existing commercially available PVA/Starch preservation membranes.