Selectively encapsulated and dry-fabricated sandwich-type patch: CO2/ClO2 differentiated dual-gas release for multi-dimensional preservation of purple cabbage.

Premature CO₂/ClO₂ loss during wet-casting fabrication bottlenecks moisture-responsive packaging scale-up. To address this, this study prepared polyacrylate nanoparticles loaded with 85.8% sodium chlorite (200-400 nm) and alginate-gelatin films (tensile strength 9.7 MPa, water vapor permeability 19.9 g·mm/m2·day·kPa). Dry nanoparticles, sodium bicarbonate, and citric acid were then loaded into alginate-gelatin pouches to create a sandwich patch, minimizing fabrication-stage gas loss. In humid environments, the polyacrylate core absorbed threefold more water than the film, driving unidirectional moisture influx. Selective encapsulation-sodium chlorite in polyacrylate/film bilayers versus sodium bicarbonate in film monolayer-enabled differentiated release: CO₂ peaked at 15% (v/v) within 12 h, while ClO₂ plateaued at 14.9 ppm (w/v) on day 3. Applied to fresh-cut purple cabbage, the differentially released gases suppressed respiration, extending shelf life from 3 to 9 days without visible wilting or decay. This dry-processing route enables multi-component gas differentiated release in smart packaging.