Chitosan/konjac glucomannan film modified with kaempferol-shellac nanoparticles for blueberry preservation

In this study, shellac nanoparticles encapsulating kaempferol (KSN) were synthesized, exhibiting a particle size of 286.23 nm and a zeta potential of −32.27 mV. KSN was subsequently incorporated into chitosan/konjac glucomannan matrices at different ratios to fabricate bioactive films (CS/KGM-KS), which were comprehensively evaluated with respect to their structural, physicochemical, mechanical, biological, and biodegradation properties. The effectiveness of the films in maintaining blueberry quality during postharvest storage was further evaluated. The results demonstrated that introducing KSN increased the film thickness and markedly improved opacity, UV–visible light barrier performance, and surface hydrophobicity. Structural and thermal characterization further revealed that hydrogen-bond interactions between KSN and the polysaccharide matrix facilitated a more homogeneous dispersion of nanoparticles, thereby enhancing film compatibility and promoting a denser, more compact structure. When the KSN dispersion was added at a 1:4 w/w ratio, the corresponding film demonstrated superior barrier and mechanical performance: the water vapor permeability and oxygen permeability decreased by 54.7% and 35.9%, respectively, compared with the control film, while the elongation at break increased by 16.18%. In addition, the incorporation of KSN substantially improved the films’ antioxidant capacity (by 9.8–41.85-fold) and antimicrobial activity (by 2.73–6.51-fold). CS/KGM-KS films significantly extended the shelf life of blueberries by suppressing microbial growth and decay, maintaining higher firmness (75.82 kg/cm 2 ), titratable acidity (0.34%), and total soluble solids (14.78%), while increasing anthocyanin content by 86.21%. Moreover, the films exhibited promising soil biodegradability. Overall, the CS/KGM-KS films exhibited strong bioactivity and provide a sustainable strategy for prolonging the storage life of perishable products.