Dual-ultrasound regulation enables co-recovery of pectin and essential oil from pomelo peel and programmable assembly of antimicrobial biodegradable films

Pomelo peel waste was valorized through an ultrasound-assisted integrated strategy to simultaneously recover pectin and essential oil for the fabrication of active biodegradable packaging films. Ultrasonic cavitation significantly promoted cell wall disruption and mass transfer, enabling the efficient co-extraction of pectin and essential oil in a single process. The essential oil was further converted into a stable nanoemulsion via ultrasonic emulsification and incorporated into a pectin/polyvinyl alcohol/carboxymethyl cellulose composite film. The physicochemical, structural, mechanical, and aroma-related properties of the films were systematically characterized by FTIR, XRD, tensile analysis, and electronic nose. The optimized film exhibited balanced mechanical performance with a tensile strength of 6.27 MPa, an elongation at break of 5.52%, and a light transmittance of 43.52%, indicating good flexibility and optical properties. Sensors responsive to nitrogen- and sulfur-containing compounds showed higher signals, likely due to oxidative transformation products rather than native sulfur volatiles. The preservation performance was evaluated using fresh strawberries as a model system. Compared with the control group, the ultrasound-enabled essential oil film effectively reduced weight loss, delayed microbial spoilage, and extended the storage life by nearly five days at room temperature. This study demonstrates that ultrasound not only intensifies the sustainable extraction of functional biopolymers but also regulates the structural assembly and release behavior of active packaging films. The proposed strategy provides a green and scalable route for converting Citrus processing waste into high-value antimicrobial packaging materials.