Edible Coating of Sodium Alginate With Gelatin Nanoparticles and Pitaya Extract (Stenocereus thurberi): Physicochemical and Antioxidant Properties

Sodium alginate is an ideal polysaccharide for food coatings, due to its gelling properties and ability to interact with bioactive compounds. The main objective of this study was to develop sodium alginate-based edible coatings incorporated with gelatin nanoparticles encapsulating pitaya extract (Stenocereus thurberi) using the coaxial electrospray technique. Nine formulations of sodium alginate at 1, 1.5, and 2 (% w/v) were tested with glycerol (1, 1.5, 2% w/v) as a plasticizer. These concentrations were chosen based on previous studies that found similar formulations to provide optimal film-forming properties without affecting color or pH. Rheological tests showed pseudoplastic behavior, typical of polysaccharide-based films. This work is novel in combining sodium alginate with gelatin nanoparticles and pitaya extract, which has been scarcely explored in the literature, improving the functional properties of coatings. Gelatin nanoparticles were obtained with and without pitaya extract, and SEM analysis revealed improvements in morphology, with average diameters of 865 nm. FTIR analysis showed interactions between sodium alginate and nanoparticles via carboxyl, amino, and hydroxyl groups. The coaxial electrospray technique was used to incorporate pitaya extract into gelatin nanoparticles, allowing precise encapsulation and controlled release of bioactive compounds. The physicochemical characterization of solutions with nanoparticles (25% and 30% w/w alginate base) showed significant differences, including decreased luminosity and pH. Zeta potential values ranged from −75.1 to −78.1 mV, indicating strong repulsion between particles, which prevents agglomeration. DPPH and ABTS radical elimination tests revealed a significant increase in antioxidant activity (p < 0.05) in formulations with coaxial nanoparticles. Compared to other formulations in the literature, these coatings exhibited superior antioxidant activity, particularly in radical scavenging. These findings demonstrate that the developed coating is a viable food coating with antioxidant properties, ideal for preserving fatty foods like meat and meat products. In conclusion, this study highlights the potential of sodium alginate-based coatings for food preservation with added antioxidant benefits.