Effect of processing conditions on the morphology and oxidative stability of lipid microcapsules during complex coacervation

The microencapsulation process of lipids by complex coacervation has been investigated in order to reach a better control of the morphology of microcapsules, and the oxidative stability of microcapsules with different morphologies was also explored. Methyl oleate was encapsulated by complex coacervation with the wall materials of gelatin and gum arabic. For improving standardization and miniaturization of microcapsules used for functional food ingredients, processing conditions of microencapsulation were optimized in order to obtain products with single oil droplets as the core materials and sizes less than oral sensory threshold of 10–25 μm. Both the stirring speed and the total wall material concentration had influence on the morphology by changing the Reynolds number (Re), which represents the turbulence level of flow system. Both the pH value and the ratio of gelatin and gum arabic could affect the morphology of final product by changing the absorbance value at 600 nm (A600 nm), which represents the agglomerated state of wall materials. A total wall material concentration of 4.00%, a stirring speed of 700 rpm, a pH of 4.20 and a ratio of gelatin to arabic gum of 1: 1 were selected as the appropriate operating parameters for the preparation of single core microcapsules. The Re value range of 1.26–1.86 × 104 and the A600 nm value greater than 0.25 were recognized as the key points for avoiding coalescence and acquiring microcapsules with single core. The change in the ratio of core to wall material had no influence on the morphology except the thickness of the wall material, which could affect the oxidative stability of core material at higher ratios of core to wall material. Considering the loading capacity and oxidative stability, 1: 1 was an ideal ratio of core to wall material.