pH-TriggeredRelease of Cinnamon Essential Oil from Sodium Alginate-Shellac Nanoparticles: Rational Design, Enhanced Stability and Antibacterial Efficacy

Sodium alginate (SA)-modified shellac nanoparticles were developed as pH-responsive carriers for cinnamon essential oil (CEO) encapsulation in aquatic product preservation. Three polyelectrolytes (SA, chitosan (CS), gelatin (Gel)) were evaluated at concentrations of 0.025–0.3% (w/v). Under pH conditions simulating spoilage (6.0–7.5), SA-SNPs exhibited superior stability with minimal changes in particle size, PDI, and zeta potential, while CS and Gel systems aggregated near their pKa values. At 0.1% SA, CEO-loaded nanoparticles (SA-SCNPs) showed excellent properties: small size (160 nm), high encapsulation efficiency (90%), and pH-triggered release (77.76% at pH 7.0 via Ritger–Peppas kinetics, n = 0.58). FT-IR confirmed ionic and hydrogen bonding between the SA and shellac. SA-SCNPs enhanced antibacterial efficacy against Shewanella putrefaciens and Pseudomonas fluorescens and maintained stability under ionic strength (300 mmol/L NaCl) and temperature variations (−18 °C to 25 °C), attributed to SA’s cryo-resistance and steric effects. This system offers a smart delivery platform for aquatic preservation.