Complex coacervation of fish gelatin and sodium alginate for clove oil microencapsulation

Clove oil (CO), rich in phenolic compounds such as eugenol, was encapsulated to enhance its stability and antimicrobial performance. Fish gelatin (FGe) and sodium alginate (SA) were used as wall materials for encapsulation through complex coacervation. Prior to encapsulation, turbidity and zeta potential were measured as a function of pH, and coacervate yield was calculated to determine optimal coacervation conditions. The FGe: SA ratios of 3:1-5:1 and pH values between 3 and 4 were determined as optimal ranges. These parameters, together with the wall-to-core ratio (wall: core), were used as independent variables in a Box-Behnken response surface methodology (RSM) to evaluate their effects on encapsulation efficiency (EE) and encapsulation yield (EY). The highest experimental EE and EY values obtained within the design were 91.7% and 89.5%, respectively. Microcapsules prepared under the optimized conditions exhibited a moisture content of 2.57%, hygroscopicity of 8.64%, and solubility of 65.33%. Thermogravimetric analysis (TGA) confirmed enhanced thermal stability, with decomposition shifting to higher temperatures (~ 200-350 °C). In the simulated gastrointestinal system, the microcapsules remained stable under acidic conditions and released CO gradually at higher pH. Antimicrobial assays showed comparable inhibition against Staphylococcus aureus and significantly higher activity against Escherichia coli compared to unencapsulated CO. These findings suggest that FGe-SA coacervate microcapsules are a promising delivery system for clove oil in functional food applications.