Comparative effects of ultrasound, ultraviolet, and microwave treatments on the structure-property relationships of cactus polysaccharide-gelatin composite films.

Biodegradable polysaccharide-protein films are promising alternatives to petroleum-based packaging but often lack adequate structural stability and functionality. Although ultrasound (US), ultraviolet (UV), and microwave (MW) treatments have been individually applied to improve biopolymer films, a systematic comparison on the same film system remains unreported. Here, cactus polysaccharide (CP) was extracted fromOpuntiaspp. with high purity (91.69% polysaccharides, 117.15 μg/g protein, 1.03 mg/g phenolics). CP-gelatin films were fabricated and treated with US (200 W, 20 kHz, 30 min), UV (254 nm, 30 W, 30 min), or MW (300 W, 2450 MHz, intermittent heating). Effects of these physical fields technologies on the structural, physicochemical, mechanical, and functional properties of the films were systematically evaluated. Compared with UV and MW treatments, US treatment resulted in significantly lower moisture content (6.38% vs. 7.09% and 6.78%), water solubility (65.34% vs. 71.51% and 68.22%), swelling index (99.0% vs. 117.7% and 108.5%), and water vapour permeability (1.81 × 10-7 vs. 2.44 × 10-7 and 2.25 × 10-7 g·m-2·Pa-1·s-1), along with the highest tensile strength (20.53 vs. 16.91 and 14.38 MPa), antioxidant activity (ABTS: 93.80% vs. 91.93% and 92.37%; DPPH: 82.48% vs. 78.29% and 81.88%), and UV-shielding performance (UV-A: 85.07% vs. 71.72% and 75.40%; UV-B: 96.99% vs. 91.37% and 93.47%).UV increased visible-light transparency but showed the lowest UV-blocking efficiency, while MW induced localized crystallization and the highest surface hydrophobicity (WCA: 87.56° vs. 74.52° for US and 76.95° for UV). All treatments slowed soil biodegradation versus control. Overall, US provided the most balanced enhancement of structural integrity, barrier performance, antioxidant activity, and UV protection, highlighting its potential for sustainable active packaging applications.