Belete,Anteneh(Dr.)Haile,Christina2025-08-132025-08-132023-01https://etd.aau.edu.et/handle/123456789/6732Complex coacervation is one of the microencapsulation techniques by which encapsulated substances release profile improved. This study was conducted by using complex coacervation to formulate and optimize microcapsules of the Cymbopogan martini essential oil. The preliminary study was conducted to define the optimal polymeric ratio for the coating materials (gelatin B and sodium alginate) and the optimal pH for coacervate by taking dry coacervate yield and turbidity as response variable. In screening study eight factors, total polymeric concentration, Palmarosa oil concentration, surfactant concentration (Tween 80), reaction time, temperature, stirring speed, crosslinker concentration (Tannic acid) and crosslinking time were screened by Plackett–Burman design generated by Minitab software using encapsulation efficiency, microcapsules surface property, microcapsules size and distribution as response variables. The three significant factors from screening design, total polymeric concentration, Palmarosa oil concentration and Surfactant concentration were further optimized by taking encapsulation as response variable, which had significant relationship with factors in screening design. Finally, the optimized microcapsules oil release was fitted to zero and first order kinetics models. The optimal polymeric ratio and optimal pH were 0.3:1 and 3.5, respectively and in the optimization study quadratic mathematical model (p < 0.0001) was an excellent fit to analyze the relationship between factors and response variable (R2, R2adj and R2 pred were > 0.9). The optimal encapsulation efficiency was 96.7% and the zero-order kinetics model (where R2 = 0.9937) was defined the oil release from microcapsules.en-USMicroencapsulationComplex coacervationPalmarosa essential oilPlackett– Burman screening designCentral composite designInvitro releaseThesis