A carboxymethyl cellulose-based pH-responsive chlorine dioxide release film for strawberry preservation

Fruit spoilage caused by microorganisms results in huge economic losses and health risks worldwide every year. To develop an intelligent antimicrobial material capable of responding to the physiological activity of postharvest fruits and releasing antibacterial agents on demand, we fabricated a pH-responsive film for the release of chlorine dioxide (ClO 2 ) using carboxymethyl cellulose (CMC) and sodium chlorite (NaClO 2 ) via the solution casting method, with a CMC:NaClO 2 ratio of 1:2 w /w. An acid environment simulated by 4 % acetic acid activated 43 % of ClO 2 released by the film within 7 days. A 1 × 2 cm 2 film in acid environment effectively inhibited the growth of Staphylococcus aureus (10 6  CFU/mL), Escherichia coli (10 5  CFU/mL), and Aspergillus niger on agar media (with colony diameters reduced from 60.00 mm to 19.07 mm). A 3 × 3 cm 2 film reduced the decay incidence caused by A. niger in strawberry from 100 % (control) to only 20 % on day 6. Compared with the control group, no significant differences in color, total soluble solids (TSSs) or triable acidity (TA) were observed in the film-treated groups. The development of pH-responsive NaClO 2 -CMC films offers a practical and effective solution for extending the shelf-life and maintaining the quality of fruit.