From Citrus Processing Residues to Functional Edible Coatings: Waste-Derived Pickering Systems for Sustainable Food Packaging and Fresh-Cut Fruit Preservation.

Fresh-cut fruits are highly susceptible to moisture loss, microbial contamination, and rapid quality deterioration during storage, creating an increasing demand for sustainable packaging technologies that can enhance product stability while reducing reliance on synthetic materials. In this study, citrus processing residues, including orange peels and fruit pomace, were valorised as a source of pectin for the development of plant-based Pickering emulsions designed for edible coating applications. Extracted pectin was modified using high-power ultrasound to tailor its physicochemical characteristics and improve its interfacial functionality. The treatment enhanced the amphiphilic nature of the biopolymer, favouring its adsorption at oil–water interfaces and enabling its use as an effective particle-stabiliser.

Modified pectin was combined with varying concentrations of zein to generate polysaccharide–protein complexes capable of stabilising concentrated oil-in-water Pickering emulsions. The influence of zein incorporation on interfacial behaviour, microstructure, antioxidant activity, colloidal stability, and rheological properties was systematically investigated. The resulting complexes promoted the formation of more homogeneous emulsion systems with improved droplet stabilisation, enhanced resistance to creaming, increased emulsifying performance, and greater antioxidant capacity. Microscopic observations revealed the formation of dense protective layers surrounding oil droplets, while rheological analyses demonstrated viscoelastic and shear-thinning behaviour indicative of stable, interconnected structures.

Selected emulsions were subsequently applied as functional edible coatings to fresh-cut pineapple for evaluating shelf-life extension and fruit quality maintenance. Coated samples exhibited lower weight loss, reduced microbial growth, and delayed quality deterioration compared with uncoated controls, successfully extending shelf-life by up to four days and demonstrating their potential as active packaging systems for fresh-cut produce.

Overall, this work presents an innovative approach for transforming fruit processing by-products into high-value coating materials that simultaneously contribute to food waste valorisation, packaging sustainability, and shelf-life extension. The developed Pickering emulsions offer a promising strategy for advancing circular food packaging solutions within sustainable food systems.